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Title:
The classification of BL Lacertae objects: the Ca H&K break
Authors:
Landt, Hermine; Padovani, Paolo; Giommi, Paolo
Journal:
Monthly Notice of the Royal Astronomical Society, Volume 336, Issue 3, pp. 945-956. (MNRAS Homepage)
Publication Date:
11/2002
Origin:
MNRAS
MNRAS Keywords:
BL Lacertae objects: general
Abstract Copyright:
(c) RAS
Bibliographic Code:
2002MNRAS.336..945L

Abstract

We investigate why BL Lacertae objects (BL Lacs) have values of the Ca H&K break (a stellar absorption feature) lower than low-power radio galaxies, and whether its use is justified to separate the two classes. For this purpose we relate this parameter to the radio and optical core emission, as well as to the X-ray powers, for a sample of ~90 radio sources. We find that the Ca H&K break value decreases with increasing jet power, and that it also anticorrelates with the radio core dominance parameter but not with extended radio emission. Based on this we conclude that the Ca H&K break value of BL Lacs and radio galaxies is a suitable indicator of orientation. From the luminosity ratios between objects with low and high Ca H&K break values we constrain the average Lorentz factors for BL Lacs and low-power radio galaxies in the radio and X-ray band to Γ~ 2-4 and derive average viewing angles for the galaxies. Our values are in agreement with results from independent methods. We find that the correlations between Ca H&K break and radio core and X-ray luminosity hold independently for low- (LBL) and high-energy peaked BL Lacs (HBL). We derive average viewing angles for their parent populations, which turn out to be similar to the ones for our entire sample, and compare for the first time the luminosities of LBL and HBL at different orientations.

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Title:
The BeppoSAX High-Energy Large-Area Survey. V. The Nature of the Hard X-Ray Source Population and Its Evolution
Authors:
La Franca, F.; Fiore, F.; Vignali, C.; Antonelli, A.; Comastri, A.; Giommi, P.; Matt, G.; Molendi, S.; Perola, G. C.; Pompilio, F.
Affiliation:
AA(Dipartimento di Fisica, Università degli Studi Roma Tre, Via della Vasca Navale 84, Rome I-00146, Italy; lafranca@fis.uniroma3.it.), AB(Osservatorio Astronomico di Roma, Via Frascati 33, Monteporzio I-00040, Italy.), AC(Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802.), AD(Osservatorio Astronomico di Roma, Via Frascati 33, Monteporzio I-00040, Italy.), AE(Osservatorio Astronomico di Bologna, Via Ranzani 1, Bologna I-40127, Italy.), AF(Agpnzia Spaziale Italiona Science Data Center, Via Galileo Galilei, Frascati I-00044, Italy.), AG(Dipartimento di Fisica, Università degli Studi Roma Tre, Via della Vasca Navale 84, Rome I-00146, Italy), AH(Istituto di Fisica Cosmica, Consiglio Nazionale delle Ricerche, Via Bassini 15, Milan I-20121, Italy.), AI(Dipartimento di Fisica, Università degli Studi Roma Tre, Via della Vasca Navale 84, Rome I-00146, Italy), AJ(International School for Advanced Studies, Via Beirut 4, Trieste I-34014, Italy.)
Journal:
The Astrophysical Journal, Volume 570, Issue 1, pp. 100-113. (ApJ Homepage)
Publication Date:
05/2002
Origin:
UCP
ApJ Keywords:
Cosmology: Observations, Galaxies: Active, Galaxies: Distances and Redshifts, Galaxies: Evolution, Galaxies: Quasars: General
Abstract Copyright:
(c) 2002: The American Astronomical Society
Bibliographic Code:
2002ApJ...570..100L

Abstract

We present optical spectroscopic identifications of hard X-ray (5-10 keV) selected sources belonging to the High-Energy Large-Area Survey sample obtained with BeppoSAX down to a 5-10 keV flux limit of f5-10keV~3×10-14 ergs cm-2 s-1. The sample consists of 118 sources. There are 25 sources that have been identified through correlations with catalogs of known sources. A spectroscopic identification for 49 more has been searched for with the telescope. The results of 13 fields were empty down to R=21. There were 37 sources identified as type 1 active galactic nuclei (AGNs) and nine as type 2 AGNs. The remaining sources are five narrow emission-line galaxies, six clusters, two BL Lac objects, one radio galaxy, and one star. Combining these objects with other hard X-ray selected AGNs from ASCA and HEAO 1, we find that the local luminosity function of type 1 AGNs (AGN 1s) in the 2-10 keV band is fairly well represented by a double power law function. There is evidence for significant cosmological evolution according to a pure luminosity evolution (PLE) model [LX(z)~(1+z)k], with k=2.12 and 2.22 (σk~=0.14) in a (Ωm,Ωλ)=(1.0,0.0) and a (Ωm,Ωλ)=(0.3,0.7) cosmology, respectively. The data show an excess of faint high-redshift type AGN 1s, which is well modeled by a luminosity-dependent density evolution (LDDE), similar to what is observed in soft X-rays. However, in both cosmologies, the statistics are not significant enough to distinguish between the PLE and LDDE models. The fitted models imply a contribution of AGN 1s to the 2-10 keV X-ray background from 35% up to 60%.

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Title:
BL Lacertae: Complex spectral variability and rapid synchrotron flare detected with BeppoSAX
Authors:
Ravasio, M.; Tagliaferri, G.; Ghisellini, G.; Giommi, P.; Nesci, R.; Massaro, E.; Chiappetti, L.; Celotti, A.; Costamante, L.; Maraschi, L.; Tavecchio, F.; Tosti, G.; Treves, A.; Wolter, A.; Balonek, T.; Carini, M.; Kato, T.; Kurtanidze, O.; Montagni, F.; Nikolashvili, M.; Noble, J.; Nucciarelli, G.; Raiteri, C. M.; Sclavi, S.; Uemura, M.; Villata, M.
Affiliation:
AA(Osservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, Italy), AB(Osservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, Italy), AC(Osservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, Italy), AD(ASI Science Data Center, Via Galileo Galilei, 00044 Frascati, Italy), AE(Dipartimento di Fisica, Universitá La Sapienza, P.le Aldo Moro 2, 00185 Roma, Italy), AF(Dipartimento di Fisica, Universitá La Sapienza, P.le Aldo Moro 2, 00185 Roma, Italy), AG(Istituto di Fisica Cosmica G.Occhialini, CNR, Via Bassini 15, 20133 Milano, Italy), AH(SISSA/ISAS, via Beirut 2-4, 34014 Trieste, Italy), AI(Osservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, Italy), AJ(Osservatorio Astronomico di Brera, Via Brera, 28, 20121 Milano, Italy), AK(Osservatorio Astronomico di Brera, Via Brera, 28, 20121 Milano, Italy), AL(Osservatorio Astronomico, Universitàdi Perugia, Via A. Pascoli, 06100 Perugia, Italy), AM(Dipartimento di Scienze, Universitàdell'Insubria, Via Valleggio 11, 22100 Como, Italy), AN(Osservatorio Astronomico di Brera, Via Brera, 28, 20121 Milano, Italy), AO(Foggy Bottom Observatory, Colgate University, 13 Oak Drive 13346, Hamilton NY, USA), AP(Dept. of Physics and Astronomy, Western Kentucky University, 1 Big Red Way, Bowling Green, KY 42102-3576, USA), AQ(Dept. of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakio-ku, Kyoto 606-8502, Japan), AR(Abastumani Astrophysical Observatory, 383762, Abastumani, Republic of Georgia), AS(Dipartimento di Fisica, Universitá La Sapienza, P.le Aldo Moro 2, 00185 Roma, Italy), AT(Abastumani Astrophysical Observatory, 383762, Abastumani, Republic of Georgia), AU(Dept. of Astronomy, Boston University, 725 Commonwealth Avenue, Boston MA 02215, USA), AV(Osservatorio Astronomico, Universitàdi Perugia, Via A. Pascoli, 06100 Perugia, Italy), AW(Osservatorio Astronomico di Torino, Strada Osservatorio 20, 10025 Pino Torinese, Italy), AX(Dipartimento di Fisica, Universitá La Sapienza, P.le Aldo Moro 2, 00185 Roma, Italy), AY(Dept. of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakio-ku, Kyoto 606-8502, Japan), AZ(Osservatorio Astronomico di Torino, Strada Osservatorio 20, 10025 Pino Torinese, Italy)
Journal:
Astronomy and Astrophysics, v.383, p.763-772 (2002) (A&A Homepage)
Publication Date:
03/2002
Origin:
A&A
A&A Keywords:
BL LACETAE OBJECTS: GENERAL, X-RAYS: GALAXIES
Abstract Copyright:
(c) 2002: Astronomy & Astrophysics
Bibliographic Code:
2002A&A...383..763R

Abstract

We report on two BeppoSAX observations of BL Lac (2200+420) performed respectively in June and December 1999, as part of a ToO program to monitor blazars in high states of activity. During both runs the source has been detected up to 100 keV, but it showed quite different spectra: in June it was concave with a very hard component above 5-6 keV (alpha1 ~ 1.6; alpha2 ~ 0.15); in December it was well fitted by a single power law (alpha ~ 0.6). During the first BeppoSAX observation BL Lac showed an astonishing variability episode: the 0.3-2 keV flux doubled in ~ 20 min, while the flux above 4 keV was almost constant. This frequency-dependent event is one of the shortest ever recorded for BL Lac objects and places lower limits on the dimension and magnetic field of the emitting region and on the energy of the synchrotron radiating electrons. A similar but less extreme behaviour is detected also in optical light curves, that display non-simultaneous, smaller fluctuations of ~ 20 % in 20 min. We fit the spectral energy distributions with a homogeneous, one-zone model to constrain the emission region in a very simple but effective SSC + external Compton scenario, highlighting the importance of the location of the emitting region with respect to the Broad Line Region and the relative spectral shape dependence. We compare our data with historical radio to gamma -ray Spectral Energy Distributions.

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Title:
Unification of Faint Radio-loud Sources: The DXRBS View
Authors:
Padovani, P.; Giommi, P.; Landt, H.; Perlman, E.
Journal:
Issues in Unification of Active Galactic Nuclei, ASP Conference Proceedings, Vol. 258. Edited by Roberto Maiolino, Alessandro Marconi, and Neil Nagar. ISBN: 1-58381-098-6. San Francisco: Astronomical Society of the Pacific, 2002., p.297
Publication Date:
00/2002
Origin:
ADS
Bibliographic Code:
2002iuag.conf..297P

Abstract

Not Available

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Title:
BeppoSAX observations of 1-Jy BL Lacertae objects - I
Authors:
Padovani, Paolo; Costamante, Luigi; Giommi, Paolo; Ghisellini, Gabriele; Comastri, Andrea; Wolter, Anna; Maraschi, Laura; Tagliaferri, Gianpiero; Megan Urry, C.
Affiliation:
AA(Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA ), AB(Università degli Studi di Milano, Milano, Italy ), AC(BeppoSAX Science Data Center, ASI, Via Corcolle 19, I-00131 Roma, Italy ), AD(Osservatorio Astronomico di Brera, Via Bianchi 46, I-23807 Merate, Italy ), AE(Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna, Italy ), AF(Osservatorio Astronomico di Brera, Via Brera 28, I-20121 Milano, Italy), AG(Osservatorio Astronomico di Brera, Via Brera 28, I-20121 Milano, Italy), AH(Osservatorio Astronomico di Brera, Via Bianchi 46, I-23807 Merate, Italy ), AI(Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA )
Journal:
Monthly Notices of the Royal Astronomical Society, Volume 328, Issue 3, pp. 931-943. (MNRAS Homepage)
Publication Date:
12/2001
Origin:
MNRAS
MNRAS Keywords:
GALAXIES: ACTIVE, BL LACERTAE OBJECTS: GENERAL, X-RAYS: GALAXIES
Abstract Copyright:
(c) 2001 The Royal Astronomical Society
Bibliographic Code:
2001MNRAS.328..931P

Abstract

We present new BeppoSAX observations of seven BL Lacertae objects selected from the 1-Jy sample plus one additional source. The collected data cover the energy range 0.1-10keV (observer's frame), reaching ~50keV for one source (BL Lac). All sources characterized by a peak in their multifrequency spectra at infrared/optical energies (i.e., of the low-energy peaked BL Lac type, LBL) display a relatively flat (αX~0.9) X-ray spectrum, which we interpret as inverse Compton emission. Four objects (two-thirds of the LBLs) show some evidence for a low-energy steepening, which is probably due to the synchrotron tail merging into the inverse Compton component around ~1-3keV. If this were generally the case with LBLs, it would explain why the 0.1-2.4keV ROSAT spectra of our sources are systematically steeper than the BeppoSAX ones (ΔαX~0.5). The broad-band spectral energy distributions fully confirm this picture, and a synchrotron inverse Compton model allows us to derive the physical parameters (intrinsic power, magnetic field, etc.) of our sources. Combining our results with those obtained by BeppoSAX on BL Lacs covering a wide range of synchrotron peak frequency, νpeak, we confirm and clarify the dependence of the X-ray spectral index on νpeak originally found in ROSAT data.

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Title:
The BeppoSAX High Energy Large Area Survey (HELLAS) - II. Number counts and X-ray spectral properties
Authors:
Fiore, F.; Giommi, P.; Vignali, C.; Comastri, A.; Matt, G.; Perola, G. C.; La Franca, F.; Molendi, S.; Tamburelli, F.; Antonelli, L. A.
Affiliation:
AA(), AB(BeppoSAX Science Data Center, Via Corcolle 19, I-00131 Roma, Italy ), AC(Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, I-40127 Bologna, Italy ; Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna, Italy ), AD(Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna, Italy ), AE(Dipartimento di Fisica, Università degli Studi `Roma Tre', Via della Vasca Navale 84, I-00146 Roma, Italy ), AF(Dipartimento di Fisica, Università degli Studi `Roma Tre', Via della Vasca Navale 84, I-00146 Roma, Italy ), AG(Dipartimento di Fisica, Università degli Studi `Roma Tre', Via della Vasca Navale 84, I-00146 Roma, Italy ), AH(IFCTR/CNR, via Bassini 15, Milano, I-20133, Italy), AI(BeppoSAX Science Data Center, Via Corcolle 19, I-00131 Roma, Italy ), AJ(Osservatorio Astronomico di Roma, Via Frascati 33, I-00044 Monteporzio, Italy )
Journal:
Monthly Notices of the Royal Astronomical Society, Volume 327, Issue 3, pp. 771-780. (MNRAS Homepage)
Publication Date:
11/2001
Origin:
MNRAS
MNRAS Keywords:
GALAXIES: ACTIVE, X-RAYS: DIFFUSE BACKGROUND, X-RAYS: GALAXIES, X-RAYS: GENERAL
Abstract Copyright:
(c) 2001 The Royal Astronomical Society
Bibliographic Code:
2001MNRAS.327..771F

Abstract

The BeppoSAX High Energy Large Area Survey (HELLAS) has surveyed about 85deg2 of sky in the 5-10keV band down to a flux of 4-5×10-14ergcm-2s-1. The source surface density of 16.9+/-6.4deg-2 at the survey limit corresponds to a resolved fraction of the 5-10keV X-ray background (XRB) of the order of 20-30 per cent. Hardness ratio analysis indicates that the spectra of a substantial fraction of the HELLAS sources (at least one-third) are harder than a αE=0.6 power law. This hardness may be caused by large absorbing columns. The hardness ratio analysis also indicates that many HELLAS sources may have a spectrum more complex than a single absorbed power law. A soft component, superimposed on a strongly cut-off power law, is likely to be present in several sources.

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Title:
Deep X-Ray Radio Blazar Survey (DXRBS). II. (Landt+, 2001)
Authors:
Landt, H.; Padovani, P.; Perlman, E. S.; Giommi, P.; Bignall, H.; Tzioumis, A.
Journal:
VizieR On-line Data Catalog: J/MNRAS/323/757. Originally published in: 2001MNRAS.323..757L
Publication Date:
11/2001
Origin:
SIMBAD
Keywords:
QSOs, BL Lac objects, Surveys, X-ray sources, Radio sources
Bibliographic Code:
2001yCat..73230757L

Abstract

We have searched the archived, pointed ROSAT Position Sensitive Proportional Counter data for blazars by correlating the WGACAT X-ray data base with several publicly available radio catalogues, restricting our candidate list to serendipitous X-ray sources with a flat radio spectrum ({alpha}r<=0.70, where S{nu}~{nu}-{alpha}). his makes up the Deep X-ray Radio Blazar Survey (DXRBS). Here we present new identifications and spectra for 106 sources, including 86 radio-loud quasars, 11 BL Lacertae objects, and nine narrow-line radio galaxies. Together with our previously published objects and already-known sources, our sample now contains 298 identified objects: 234 radio-loud quasars [181 flat-spectrum quasars: FSRQ ({alpha}r<=0.50) and 53 steep-spectrum quasars: SSRQ], 36 BL Lacs and 28 narrow-line radio galaxies. Redshift information is available for 96 per cent of these. Thus our selection technique is ~90 per cent efficient at finding radio-loud quasars and BL Lacs. Reaching 5-GHz radio fluxes ~50mJy and 0.1-2.0keV X-ray fluxes a few W10-14erg/cm2/s, DXRBS is the faintest and largest flat-spectrum radio sample with nearly complete (~85 per cent) identification. (3 data files).

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Title:
Extreme synchrotron BL Lac objects. Stretching the blazar sequence
Authors:
Costamante, L.; Ghisellini, G.; Giommi, P.; Tagliaferri, G.; Celotti, A.; Chiaberge, M.; Fossati, G.; Maraschi, L.; Tavecchio, F.; Treves, A.; Wolter, A.
Affiliation:
AA(Osservatorio Astron. di Brera, via Bianchi 46 Merate, Italy; Universitàdegli Studi di Milano, via Celoria 16 Milano, Italy), AB(Osservatorio Astron. di Brera, via Bianchi 46 Merate, Italy), AC(A.S.I., Science Data Center, c/o ESA-ESRIN, via G. Galilei, Frascati, Italy), AD(Osservatorio Astron. di Brera, via Bianchi 46 Merate, Italy), AE(SISSA/ISAS, via Beirut 2-4 Trieste, Italy), AF(SISSA/ISAS, via Beirut 2-4 Trieste, Italy), AG(CASS, University of California, San Diego, CA 92093-0494, USA), AH(Osservatorio Astron. di Brera, via Brera 28 Milano, Italy), AI(Osservatorio Astron. di Brera, via Brera 28 Milano, Italy), AJ(Universitàdell'Insubria, via Valleggio 11 Como, Italy), AK(Osservatorio Astron. di Brera, via Brera 28 Milano, Italy)
Journal:
Astronomy and Astrophysics, v.371, p.512-526 (2001) (A&A Homepage)
Publication Date:
05/2001
Origin:
A&A
A&A Keywords:
BL LACERTAE OBJECTS: INDIVIDUAL: 1ES 0033+595, 1ES 0120+340, PKS 0548-322, GB 1114+203, 1ES 1218+304, 1ES 1426+428, H 2356-309, X-RAYS: GENERAL, TEV: GENERAL
Abstract Copyright:
(c) 2001: Astronomy & Astrophysics
Bibliographic Code:
2001A&A...371..512C

Abstract

We performed an observational program with the X-ray satellite BeppoSAX, to study objects with extreme synchrotron peak frequencies (nupeak >1 keV). Of the seven sources observed, five revealed or confirmed their extreme nature. Four showed peak frequencies in the range 1-5 keV, while one (1ES 1426+428) displayed a flat power law spectrum (alphax =0.92+/-0.04) which locates its synchrotron peak at or above 100 keV. This is the third source of this type ever found, after Mkn 501 and 1ES 2344+514. In the context of the whole blazar class, the broad band properties of these objects confirm the scenario of a synchrotron peak smoothly spanning the IR - X-ray range, which explains the multi-frequency properties of the blazar class. Our data also confirm the large nupeak variability which seems to characterize this class of sources, compared with lower nupeak objects. Given the high synchrotron peak energies, which flag the presence of high energy electrons, these extreme BL Lacs are also good candidates for TeV emission, and therefore good probes of the IR background.

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Title:
The Deep X-Ray Radio Blazar Survey (DXRBS) - II. New identifications
Authors:
Landt, Hermine; Padovani, Paolo; Perlman, Eric S.; Giommi, Paolo; Bignall, Hayley; Tzioumis, Anastasios
Affiliation:
AA(Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA; Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg, Germany), AB(Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA), AC(Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA), AD(BeppoSAX Science Data Center, ASI, Via Corcolle 19, I-00131 Roma, Italy), AE(Department of Physics and Mathematical Physics, University of Adelaide, SA 5005, Australia), AF(Australia Telescope National Facility, CSIRO, PO Box 76, Epping, NSW 2121, Australia)
Journal:
Monthly Notices of the Royal Astronomical Society, Volume 323, Issue 3, pp. 757-784. (MNRAS Homepage)
Publication Date:
05/2001
Origin:
MNRAS
MNRAS Keywords:
SURVEYS, BL LACERTAE OBJECTS: GENERAL, QUASARS: GENERAL, RADIO CONTINUUM: GALAXIES, X-RAYS: GALAXIES
Abstract Copyright:
(c) 2001 The Royal Astronomical Society
Bibliographic Code:
2001MNRAS.323..757L

Abstract

We have searched the archived, pointed ROSAT Position Sensitive Proportional Counter data for blazars by correlating the WGACAT X-ray data base with several publicly available radio catalogues, restricting our candidate list to serendipitous X-ray sources with a flat radio spectrum (αr<=0.70, where Sν~ν-α). This makes up the Deep X-ray Radio Blazar Survey (DXRBS). Here we present new identifications and spectra for 106 sources, including 86 radio-loud quasars, 11 BL Lacertae objects, and nine narrow-line radio galaxies. Together with our previously published objects and already-known sources, our sample now contains 298 identified objects: 234 radio-loud quasars [181 flat-spectrum quasars: FSRQ (αr<=0.50) and 53 steep-spectrum quasars: SSRQ], 36 BL Lacs and 28 narrow-line radio galaxies. Redshift information is available for 96 per cent of these. Thus our selection technique is ~90 per cent efficient at finding radio-loud quasars and BL Lacs. Reaching 5-GHz radio fluxes ~50mJy and 0.1-2.0keV X-ray fluxes a few ×10-14ergcm-2s-1, DXRBS is the faintest and largest flat-spectrum radio sample with nearly complete (~85 per cent) identification. We review the properties of the DXRBS blazar sample, including redshift distribution and coverage of the X-ray-radio-power plane for quasars and BL Lacs. Additionally, we touch upon the expanded multiwavelength view of blazars provided by DXRBS. By sampling for the first time the faint end of the radio and X-ray luminosity functions, this sample will allow us to investigate the blazar phenomenon and the validity of unified schemes down to relatively low powers.

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Title:
The 0.1-200 keV spectrum of the blazar PKS 2005-489 during an active state
Authors:
Tagliaferri, G.; Ghisellini, G.; Giommi, P.; Celotti, A.; Chiaberge, M.; Chiappetti, L.; Glass, I. S.; Maraschi, L.; Tavecchio, F.; Treves, A.; Wolter, A.
Affiliation:
AA(Osservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, Italy), AB(Osservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, Italy), AC(BeppoSAX Science Data Center, ASI, Via Corcolle, 19, 00131 Roma, Italy), AD(SISSA/ISAS, via Beirut 2-4, 34014 Trieste, Italy), AE(SISSA/ISAS, via Beirut 2-4, 34014 Trieste, Italy), AF(Istituto di Fisica Cosmica G.Occhialini, CNR, Via Bassini 15, 20133 Milano, Italy), AG(South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa), AH(Osservatorio Astronomico di Brera, Via Brera, 28, 20121 Milano, Italy), AI(Osservatorio Astronomico di Brera, Via Brera, 28, 20121 Milano, Italy), AJ(Istituto di Fisica, Universitàdell'Insubria, Via Lucini 3, 22100 Como, Italy), AK(Osservatorio Astronomico di Brera, Via Brera, 28, 20121 Milano, Italy)
Journal:
Astronomy and Astrophysics, v.368, p.38-43 (2001) (A&A Homepage)
Publication Date:
03/2001
Origin:
A&A
A&A Keywords:
BL LACERTAE OBJECTS: GENERAL, X-RAYS: GALAXIES, BL LACERTAE OBJECTS: INDIVIDUAL: PKS 2005-489
Abstract Copyright:
(c) 2001: Astronomy & Astrophysics
Bibliographic Code:
2001A&A...368...38T

Abstract

The bright BL Lac object PKS 2005-489 was observed by BeppoSAX on November 1-2, 1998, following an active X-ray state detected by RossiXTE. The source, detected between 0.1 and 200 keV, was in a very high state with a continuum well fitted by a steepening spectrum due to synchrotron emission only. Our X-ray spectrum is the flattest ever observed for this source. The different X-ray spectral slopes and fluxes, as measured by various satellites, are consistent with relatively little changes of the peak frequency of the synchrotron emission, always located below 1017 Hz. We discuss these results in the framework of synchrotron self-Compton models. We found that for the BeppoSAX observation, the synchrotron peak frequency is between 1015 and 2.5 1016 Hz, depending on the model assumptions.

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Title:
Multiwaveband studies of the hard ROSAT SMC transient 1WGA J0053.8-7226: a new X-ray pulsar
Authors:
Buckley, D. A. H.; Coe, M. J.; Stevens, J. B.; van der Heyden, K.; Angelini, L.; White, N.; Giommi, P.
Affiliation:
AA(South African Astronomical Observatory, P.O. Box 9, Observatory 7935, Cape Town, South Africa ), AB(Physics and Astronomy Department, The University, Southampton SO17 3BJ ), AC(Physics and Astronomy Department, The University, Southampton SO17 3BJ ), AD(South African Astronomical Observatory, P.O. Box 9, Observatory 7935, Cape Town, South Africa ), AE(HEASARC, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA), AF(HEASARC, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA), AG(HEASARC, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA)
Journal:
Monthly Notices of the Royal Astronomical Society, Volume 320, Issue 2, pp. 281-288. (MNRAS Homepage)
Publication Date:
01/2001
Origin:
MNRAS
MNRAS Keywords:
BINARIES: GENERAL, STARS: EMISSION-LINE, BE, PULSARS: GENERAL, INFRARED: STARS, X-RAYS: STARS
Abstract Copyright:
(c) 2001 The Royal Astronomical Society
Bibliographic Code:
2001MNRAS.320..281B

Abstract

We report on two optical candidates for the counterpart to an X-ray source in the Small Magellanic Cloud, 1WGA J0053.8-7226, identified as a serendipitous X-ray source from the ROSAT Position Sensitive Proportional Counter (PSPC) archive, and also observed by the Einstein Imaging Proportional Counter. Its X-ray properties, namely the hard X-ray spectrum, flux variability and column density, indicate a hard, transient source, with a luminosity of ~ 3.8×1035ergs-1. XTE and ASCA observations have confirmed the source to be an X-ray pulsar, with a 46-s spin period. Our optical observations reveal two possible candidates within the error circle. Both exhibit strong Hα and weaker Hβ emission. The optical colours indicate that both objects are Be-type stars. The Be nature of the stars implies that the counterpart is most likely a Be/X-ray binary system. Subsequent infrared (IR) photometry (JHK) of one of the objects shows that the source varies by at least 0.5mag, while the (J-K) measured nearly simultaneously with the UBVRI and spectroscopic observations indicate an IR excess of ~0.3mag.

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Title:
The log N-log S relationship from the BeppoSAX 2-10 keV survey
Authors:
Perri, M.; Giommi, P.; Fiore, F.
Journal:
Memorie della Società Astronomica Italiana (ISSN 0037-8720), Vol. 72, N. 1, p. 203 - 205 (2001). In: AGN in the year 2000. Fourth National Meeting on Active Galactic Nuclei, Trieste, 15 - 18 May 2000, edited by A. Celotti
Publication Date:
00/2001
Origin:
ARI
Keywords:
X-Ray Surveys
Abstract Copyright:
SAIt
Bibliographic Code:
2001MmSAI..72..203P

Abstract

The results of a 2 - 10 keV BeppoSAX X-ray survey based on 140 high galactic latitude MECS fields are presented. About 25% of the Cosmic X-ray Background (CXB) is resolved into discrete sources at the sensitivity limit of the survey (S ~ 5×10-14 erg cm-2 s-1). The log N-log S relationship, built with the 177 X-ray sources of the survey, is steep and in good agreement with that derived from ASCA surveys. The results of a CXB fluctuation analysis, which probes the log N-log S down to about 1×10-14 erg cm-2 s-1, are also presented.

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Title:
BL Lacs at the Blue End of the Blazar Sequence
Authors:
Costamante, L.; Ghisellini, G.; Wolter, A.; Tagliaferri, G.; Fossati, G.; Padovani, P.; Giommi, P.
Journal:
Blazar Demographics and Physics, ASP Conference Series, Vol. 227. Edited by Paolo Padovani and C. Megan Urry. San Francisco: Astronomical Society of the Pacific. ISBN: 1-58381-059-5, p.135
Publication Date:
00/2001
Origin:
ADS
Bibliographic Code:
2001bdp..conf..135C

Abstract

Not Available

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Title:
The BeppoSAX SOC short GRB project
Authors:
Coletta, A.; Smith, M. J. S.; Gandolfi, G.; Celidonio, G.; Costa, E.; D'Andreta, G.; di Ciolo, L.; Feroci, M.; Frontera, F.; Giommi, P.; Guidorzi, C.; Heise, J.; Muller, J. M.; Paolino, A.; Piro, L.; Ricci, D.; Tarei, G.; Tassone, G.
Journal:
Memorie della Società Astronomica Italiana (ISSN 0037-8720), Vol. 72, N. 4, p. 845 - 848 (2001). In: 44th Annual Meeting of the Italian Astronomical Society. Monte Porzio Catone, 10 - 15 April 2000, edited by L. A. Antonelli, G. Bono, G. Giobbi, N. Menci
Publication Date:
00/2001
Origin:
ARI
Keywords:
Gamma-Ray Bursts
Abstract Copyright:
SAIt
Bibliographic Code:
2001MmSAI..72..845C

Abstract

One of the most intriguing mysteries of the Gamma Ray Burst (GRB) phenomena is their bimodal duration distribution, originally found in C-GRO/Batse data. This separates GRBs in two classes of events, shorter and longer than 2 seconds. The bimodality suggests different emission sites and processes or even different physical models for the central engine of the burst, but its orgin is yet to be explained coherently. Recent results however have shown that the BeppoSAX Gamma Ray Burst Monitor (GRBM) is certainly sensitive enough to detect a large proportion of short events and that under certain circumstances their position may be determined using the BeppoSAX Wide Field Cameras (WFCs). We present the results of a real time research relevant to short GRBs being performed at the BeppoSAX Scientific Operation Center in parallel with archive analysis carried out in collaboration with BeppoSAX Scientific Data Center, IAS/CNR, TESRE/CNR, University of Ferrara and SRON.

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Title:
Looking for high energy peaked blazars
Authors:
Costamante, L.; Ghisellini, G.; Celotti, A.; Giommi, P.; Padovani, P.; Tagliaferri, G.; Wolter, A.; Chiaberge, M.; Fossati, G.; Pian, E.; Maraschi, L.; Tavecchio, F.; Treves, A.
Journal:
Memorie della Società Astronomica Italiana (ISSN 0037-8720), Vol. 72, N. 1, p. 153 - 155 (2001). In: AGN in the year 2000. Fourth National Meeting on Active Galactic Nuclei, Trieste, 15 - 18 May 2000, edited by A. Celotti
Publication Date:
00/2001
Origin:
ARI
Keywords:
Blazars, High Energy
Abstract Copyright:
SAIt
Bibliographic Code:
2001MmSAI..72..153C

Abstract

Blazars can be classified on the basis of their overall Spectral Energy Distribution (SED). BL Lac objects are usually divided in LBL or HBL (Low or High energy peaked BL Lacs), according to the peak frequency of the synchrotron emission, if in the optical or UV-soft-X band respectively. FSRQs instead are characterized by synchrotron peaks mainly at IR-optical frequencies, similarly to LBLs. Here we report on recent BeppoSAX observations which are unveiling the high energy branch of the range of synchrotron peak frequencies. Four new "extreme" HBLs have been discovered, one of which (1ES 1426+428) peaks near or above 100 keV, in a quiescent state.

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Title:
The BeppoSAX GRATIS Survey
Authors:
Perri, M.; Giommi, P.; Fiore, F.; Capalbi, M.
Journal:
X-ray astronomy : stellar endpoints, AGN, and the diffuse X-ray background, proceedings of a conference held in Bologna, Italy, 6-10 September 1999. Published by Melville, NY: American Institute of Physics, 2001. xvii, 1041 p. Edited by Nicholas E. White, Giuseppe Malaguti, and Giorgio G.C. Palumbo. AIP conference proceedings, Vol. 599. ISBN 0735400431, p.858
Publication Date:
00/2001
Origin:
ADS
Bibliographic Code:
2001xase.conf..858P

Abstract

Not Available

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Title:
The Cosmological Evolution of BL Lacertae Objects
Authors:
Giommi, P.; Pellizzoni, A.; Perri, M.; Padovani, P.
Journal:
Blazar Demographics and Physics, ASP Conference Series, Vol. 227. Edited by Paolo Padovani and C. Megan Urry. San Francisco: Astronomical Society of the Pacific. ISBN: 1-58381-059-5, p.227
Publication Date:
00/2001
Origin:
ADS
Bibliographic Code:
2001bdp..conf..227G

Abstract

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Title:
BeppoSAX Observations of Markarian 501 in June 1999
Authors:
Pian, E.; Chiappetti, L.; Giommi, P.; Tavecchio, F.; Maraschi, L.; Palazzi, E.; Aharonian, F.; Catanese, M.; Celotti, A.; Degrange, B.; Djannati-Atai, A.; Fossati, G.; Ghisellini, G.; Krawczynski, H.; Raiteri, C. M.; Sambruna, R. M.; Smith, D.; Tagliaferri, G.; Tosti, G.; Treves, A.; Urry, C. M.; Villata, M.
Journal:
X-ray astronomy : stellar endpoints, AGN, and the diffuse X-ray background, proceedings of a conference held in Bologna, Italy, 6-10 September 1999. Published by Melville, NY: American Institute of Physics, 2001. xvii, 1041 p. Edited by Nicholas E. White, Giuseppe Malaguti, and Giorgio G.C. Palumbo. AIP conference proceedings, Vol. 599. ISBN 0735400431, p.866
Publication Date:
00/2001
Origin:
ADS
Bibliographic Code:
2001xase.conf..866P

Abstract

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Title:
Simultaneous Optical and X-Ray Observations of BL Lacertae
Authors:
Nesci, R.; Massaro, E.; Montagni, F.; Sclavi, S.; Balonek, T.; Caler, M.; Tremonti, C.; D'Alessio, F.; Catalano, S.; Frasca, A.; Marilli, E.; Tagliaferri, G.; Ghisellini, G.; Ravasio, M.; Giommi, P.; Chiappetti, L.; Kato, T.; Uemura, M.; Kurtanidze, O. M.; Nikolashvili, M. G.; Carini, M. T.; Noble, J. C.; Tosti, G.; Nucciarelli, G.; Mattox, J.
Journal:
Blazar Demographics and Physics, ASP Conference Series, Vol. 227. Edited by Paolo Padovani and C. Megan Urry. San Francisco: Astronomical Society of the Pacific. ISBN: 1-58381-059-5, p.144
Publication Date:
00/2001
Origin:
ADS
Bibliographic Code:
2001bdp..conf..144N

Abstract

Not Available

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Title:
The BeppoSAX HELLAS Survey: On the Nature of Faint Hard X-ray Selected Sources
Authors:
Fiore, F.; Antonelli, L. A.; Ciliegi, P.; Comastri, A.; Giommi, P.; La Franca, F.; Maiolino, R.; Matt, G.; Molendi, S.; Perola, G. C.; Vignali, C.
Journal:
X-ray astronomy : stellar endpoints, AGN, and the diffuse X-ray background, proceedings of a conference held in Bologna, Italy, 6-10 September 1999. Published by Melville, NY: American Institute of Physics, 2001. xvii, 1041 p. Edited by Nicholas E. White, Giuseppe Malaguti, and Giorgio G.C. Palumbo. AIP conference proceedings, Vol. 599. ISBN 0735400431, p.111
Publication Date:
00/2001
Origin:
ADS
Bibliographic Code:
2001xase.conf..111F

Abstract

Not Available

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Title:
Two BeppoSAX observations of BL Lac
Authors:
Tagliaferri, G.; Ghisellini, G.; Ravasio, M.; Celotti, A.; Chiaberge, M.; Chiappetti, L.; Costamante, L.; Giommi, P.; Maraschi, L.; Massaro, E.; Nesci, R.; Raiteri, C. M.; Tavecchio, F.; Tosti, G.; Treves, A.; Villata, M.; Wolter, A.
Journal:
Memorie della Società Astronomica Italiana (ISSN 0037-8720), Vol. 72, N. 1, p. 135 - 137 (2001). In: AGN in the year 2000. Fourth National Meeting on Active Galactic Nuclei, Trieste, 15 - 18 May 2000, edited by A. Celotti
Publication Date:
00/2001
Origin:
ARI
Keywords:
BL Lacertae Objects, X Rays
Abstract Copyright:
SAIt
Bibliographic Code:
2001MmSAI..72..135T

Abstract

We present the results of two ToO BeppoSAX observations of BL Lac. During the first observation we detected both the synchrotron and the Compton components. Fast time variability was present, but only for the synchrotron component. During the second observation the spectrum was flatter and only the Compton component was present. Four different SED are presented and can be described by a blob moving along a jet and responsible for the SSC emission. The seed photons for the Compton scattering are the synchrotron photons themself plus possibly external photons coming from the broad line region.

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Title:
New Extreme Synchrotron BL Lac Objects
Authors:
Costamante, L.; Ghisellini, G.; Giommi, P.; Tagliaferri, G.; Celotti, A.; Chiaberge, M.; Chiappetti, L.; Fossati, G.; Maraschi, L.; Tavecchio, F.; Treves, A.; Wolter, A.
Journal:
X-ray astronomy : stellar endpoints, AGN, and the diffuse X-ray background, proceedings of a conference held in Bologna, Italy, 6-10 September 1999. Published by Melville, NY: American Institute of Physics, 2001. xvii, 1041 p. Edited by Nicholas E. White, Giuseppe Malaguti, and Giorgio G.C. Palumbo. AIP conference proceedings, Vol. 599. ISBN 0735400431, p.586
Publication Date:
00/2001
Origin:
ADS
Bibliographic Code:
2001xase.conf..586C

Abstract

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Title:
The AGN content of the BeppoSAX MECS source catalog
Authors:
Capalbi, Milvia; Giommi, Paolo
Journal:
Memorie della Società Astronomica Italiana (ISSN 0037-8720), Vol. 72, N. 1, p. 197 - 198 (2001). In: AGN in the year 2000. Fourth National Meeting on Active Galactic Nuclei, Trieste, 15 - 18 May 2000, edited by A. Celotti
Publication Date:
00/2001
Origin:
ARI
Keywords:
Active Galactic Nuclei, Energy Distribution
Abstract Copyright:
SAIt
Bibliographic Code:
2001MmSAI..72..197C

Abstract

We selected the AGN observations contained in the public archive of the BeppoSAX 2 - 10 keV MECS sources and we are performing a detailed systematic study of their properties. We are constructing the Spectral Energy Distribution of many objects belonging to different subclasses to investigate their broad band characteristics. We are also studying their fluxes and other parameters connected to their spectral properties.

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Title:
The Emission Line Properties of DXRBS Blazars
Authors:
Landt, H.; Padovani, P.; Perlman, E. S.; Giommi, P.
Journal:
Blazar Demographics and Physics, ASP Conference Series, Vol. 227. Edited by Paolo Padovani and C. Megan Urry. San Francisco: Astronomical Society of the Pacific. ISBN: 1-58381-059-5, p.73
Publication Date:
00/2001
Origin:
ADS
Bibliographic Code:
2001bdp..conf...73L

Abstract

Not Available

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Title:
Mining the Blazar Sky
Authors:
Padovani, P.; Giommi, P.
Journal:
Mining the Sky, Proceedings of the MPA/ESO/MPE Workshop held at Garching, Germany, 31 July-4 August, 2000. Edited by A. J. Banday, S. Zaroubi, and M. Bartelmann. Heidelberg: Springer-Verlag, 2001., p.494
Publication Date:
00/2001
Origin:
ADS
Bibliographic Code:
2001misk.conf..494P

Abstract

Not Available

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Title:
Synchrotron and Compton Components and Their Variability in BL Lac Objects
Authors:
Giommi, P.; Ghisellini, G.; Padovani, P.; Tagliaferri, G.
Journal:
X-ray astronomy : stellar endpoints, AGN, and the diffuse X-ray background, proceedings of a conference held in Bologna, Italy, 6-10 September 1999. Published by Melville, NY: American Institute of Physics, 2001. xvii, 1041 p. Edited by Nicholas E. White, Giuseppe Malaguti, and Giorgio G.C. Palumbo. AIP conference proceedings, Vol. 599. ISBN 0735400431, p.441
Publication Date:
00/2001
Origin:
ADS
Bibliographic Code:
2001xase.conf..441G

Abstract

Not Available

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Title:
Surveys and the Blazar Parameter Space
Authors:
Perlman, E. S.; Padovani, P.; Landt, H.; Stocke, J. T.; Costamante, L.; Rector, T.; Giommi, P.; Schachter, J. F.
Journal:
Blazar Demographics and Physics, ASP Conference Series, Vol. 227. Edited by Paolo Padovani and C. Megan Urry. San Francisco: Astronomical Society of the Pacific. ISBN: 1-58381-059-5, p.200
Publication Date:
00/2001
Origin:
ADS
Bibliographic Code:
2001bdp..conf..200P

Abstract

Not Available

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Title:
Flaring Blazars with BeppoSAX
Authors:
Tagliaferri, G.; Ghisellini, G.; Giommi, P.; Chiappetti, L.; Maraschi, L.; Celotti, A.; Chiaberge, M.; Comastri, A.; Costamante, L.; Fossati, G.; Massaro, E.; Nesci, R.; Pian, E.; Raiteri, C. M.; Ravasio, M.; Tavecchio, F.; Tosti, G.; Treves, A.; Villata, M.; Wolter, A.
Journal:
X-ray astronomy : stellar endpoints, AGN, and the diffuse X-ray background, proceedings of a conference held in Bologna, Italy, 6-10 September 1999. Published by Melville, NY: American Institute of Physics, 2001. xvii, 1041 p. Edited by Nicholas E. White, Giuseppe Malaguti, and Giorgio G.C. Palumbo. AIP conference proceedings, Vol. 599. ISBN 0735400431, p.971
Publication Date:
00/2001
Origin:
ADS
Bibliographic Code:
2001xase.conf..971T

Abstract

Not Available

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Title:
The BeppoSAX 2-10 keV Survey (Giommi+, 2000)
Authors:
Giommi, P.; Perri, M.; Fiore, F.
Journal:
VizieR On-line Data Catalog: J/A+A/362/799. Originally published in: 2000A&A...362..799G
Publication Date:
11/2000
Origin:
SIMBAD
Keywords:
X-ray sources, Galaxy catalogs, Surveys
Bibliographic Code:
2000yCat..33620799G

Abstract

File table contains the name of the sources, their coordinates (J2000.0) and the measured flux detected by the BeppoSAX MECS instrument in the 2-10 keV energy band. Additional information (other designation, class and redshift) if available in literature is also provided. (1 data file).

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Title:
GRB 001109
Authors:
Amati, L.; Frontera, F.; Pian, E.; Giommi, P.; Capalbi, M.; Costa, E.; Gandolfi, G.; in 't Zand, J. J. M.; Guidorzi, C.; Granata, S.; Paolino, A.
Journal:
IAU Circ., 7519, 1 (2000). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
11/2000
Origin:
CBAT
Objects:
GRB 001109
Bibliographic Code:
2000IAUC.7519....1A

Abstract

IAUC 7519 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
Extragalactic 2-10 keV source counts from a fluctuation analysis of deep BeppoSAX MECS images
Authors:
Perri, M.; Giommi, P.
Affiliation:
AA(BeppoSAX Science Data Center, ASI, Via Corcolle, 19, 00131 Roma, Italy; Universitàdi Roma ``Tor Vergata'', Dipartimento di Fisica, Via della Ricerca Scientifica, 1, 00133 Roma, Italy), AB(BeppoSAX Science Data Center, ASI, Via Corcolle, 19, 00131 Roma, Italy)
Journal:
Astronomy and Astrophysics, v.362, p.L57-L62 (2000) (A&A Homepage)
Publication Date:
10/2000
Origin:
A&A
A&A Keywords:
METHODS: STATISTICAL, GALAXIES: ACTIVE, COSMOLOGY: DIFFUSE RADIATION, X-RAYS: GENERAL
Abstract Copyright:
(c) 2000: Astronomy & Astrophysics
Bibliographic Code:
2000A&A...362L..57P

Abstract

We present an analysis of the spatial fluctuations of the 2-10 keV Cosmic X-ray Background (CXB) as measured from 22 high galactic latitude (|b| > 25degr ) fields observed with the MECS instrument on-board BeppoSAX. This technique allowed us to probe extragalactic source counts a factor 3-4 fainter than is possible with direct measurements of pointlike sources in MECS deep fields. The slope of the 2-10 keV logN-logS relationship is found to be still close to the ``Euclidean'' one (gamma = 1.5) down to our flux limit of ~ 1.5*E-14 erg cm-2 s-1 , where the contribution of discrete sources to the 2-10 keV CXB amounts to ~ 40-50%. Source counts derived from the analysis presented in this letter are in very good agreement both with those directly measured with ASCA and BeppoSAX deep surveys at bright fluxes and with a first estimation of the 2-10 keV Chandra logN-logS at fainter fluxes.

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Title:
Detection of exceptional X-ray spectral variability in the TeV BL Lac 1ES 2344+514
Authors:
Giommi, P.; Padovani, P.; Perlman, E.
Affiliation:
AA(BeppoSAX Science Data Center, ASI, Via Corcolle, 19 I-00131 Roma, Italy ), AB(Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 U.S.A), AC(Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 U.S.A)
Journal:
Monthly Notices of the Royal Astronomical Society, Volume 317, Issue 4, pp. 743-749. (MNRAS Homepage)
Publication Date:
10/2000
Origin:
MNRAS
MNRAS Keywords:
GALAXIES: ACTIVE, BL LACERTAE OBJECTS: INDIVIDUAL: 1ES 2344+514, X-RAYS: GALAXIES
Abstract Copyright:
(c) 2000 The Royal Astronomical Society
Bibliographic Code:
2000MNRAS.317..743G

Abstract

We present the results of six BeppoSAX observations of 1ES 2344+514, five of which were taken within one week. 1ES 2344+514, one of the few known TeV BL Lac objects, was detected by the BeppoSAX Narrow Field Instruments (NFI) in the range 0.1 and ~50keV. During the first five closely spaced observations 1ES 2344+514 showed large-amplitude luminosity variability, associated with spectacular spectral changes: in particular, the last observation found the source to be several times fainter, with a much steeper X-ray spectrum. The energy-dependent shape of the light curve and the spectral changes both imply a large frequency shift (by a factor of 30 or more) of the peak of synchrotron emission. At maximum flux the peak was located at, or above, 10keV, making 1ES 2344+514 the second blazar (after Mrk 501) to have a synchrotron peak in the hard X-ray band. The frequency shift, and the corresponding increase in luminosity, might be caused by the onset of a second synchrotron component extending from the soft to the hard X-ray band where most of the power is emitted. Rapid variability on a time-scale of approximately 5000s has also been detected when the source was brightest.

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Title:
The BeppoSAX 2-10 keV survey
Authors:
Giommi, P.; Perri, M.; Fiore, F.
Affiliation:
AA( BeppoSAX Science Data Center, ASI, Via Corcolle 19, 00131 Roma, Italy), AB( BeppoSAX Science Data Center, ASI, Via Corcolle 19, 00131 Roma, Italy), AC( BeppoSAX Science Data Center, ASI, Via Corcolle 19, 00131 Roma, Italy; Osservatorio Astronomico di Roma, Via Frascati 33, 00044 Monteporzio, Italy; Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA)
Journal:
Astronomy and Astrophysics, v.362, p.799-808 (2000) (A&A Homepage)
Publication Date:
10/2000
Origin:
A&A
A&A Keywords:
SURVEYS, COSMOLOGY: OBSERVATIONS, X-RAYS: GALAXIES, X-RAYS: GENERAL
Abstract Copyright:
(c) 2000: Astronomy & Astrophysics
Bibliographic Code:
2000A&A...362..799G

Abstract

We present the results of a 2-10 keV BeppoSAX survey based on 140 high galactic latitude MECS fields, 12 of which are deep exposures of ``blank'' parts of the sky. The limiting sensitivity is 5*E-14 erg cm -2s-1 where about 25% of the Cosmic X-ray Background (CXB) is resolved into discrete sources. The logN-logS function, built with a statistically complete sample of 177 sources, is steep and in good agreement with the counts derived from ASCA surveys. A CXB fluctuation analysis allowed us to probe the logN-logS down to about 1.5*E-14 erg cm -2s-1 where the contribution of discrete sources to the CXB grows to ~ 40-50%. A hardness ratio analysis reveals the presence of a wide range of spectral shapes and that a fairly large fraction of sources appear to be heavily absorbed, some of which showing soft components. A comparison of the flux distribution of different subsamples confirms the existence of a spectral hardening with decreasing flux. This effect is probably due to an increasing percentage of absorbed sources at faint fluxes, rather than to a gradual flattening of the spectral slope. Nearly all the sources for which adequate ROSAT exposures exist, have been detected in the soft X-rays. This confirms that soft spectral components are present even in strongly absorbed objects, and that a large population of sources undetectable below a few keV does not exist. A Ve/Va test provides evidence for the presence of cosmological evolution of a magnitude similar to that found in soft X-ray extragalactic sources. Evolution is present both in normal and absorbed sources, with the latter population possibly evolving faster, although this effect could also be the result of complex selection effects. Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

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Title:
Prompt and Afterglow Emission from the X-Ray-Rich GRB 981226 Observed withBeppoSAX
Authors:
Frontera, F.; Antonelli, L. A.; Amati, L.; Montanari, E.; Costa, E.; Dal Fiume, D.; Giommi, P.; Feroci, M.; Gennaro, G.; Heise, J.; Masetti, N.; Muller, J. M.; Nicastro, L.; Orlandini, M.; Palazzi, E.; Pian, E.; Piro, L.; Soffitta, P.; Stornelli, M.; in 't Zand, J. J. M.; Frail, D. A.; Kulkarni, S. R.; Vietri, M.
Affiliation:
AA(Dipartimento di Fisica, Università di Ferrara, Via Paradiso 12, 44100 Ferrara, Italy.; Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, 40129 Bologna, Italy), AB(Osservatorio Astronomico di Roma, Via Frascati, 33, 00040 Monteporzio Catone (RM), Italy), AC(Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, 40129 Bologna, Italy), AD(Dipartimento di Fisica, Università di Ferrara, Via Paradiso 12, 44100 Ferrara, Italy), AE(Istituto Astrofisica Spaziale, C.N.R., Via Fosso del Cavaliere, 00133 Roma, Italy), AF(Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, 40129 Bologna, Italy), AG(BeppoSAX Scientific Data Center, Via Corcolle 19, 00131 Roma, Italy), AH(Istituto Astrofisica Spaziale, C.N.R., Via Fosso del Cavaliere, 00133 Roma, Italy), AI(BeppoSAX Operative Control Center, Via Corcolle 19, 00131 Roma, Italy), AJ(Space Research Organization in the Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, Netherlands), AK(Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, 40129 Bologna, Italy), AL(BeppoSAX Scientific Data Center, Via Corcolle 19, 00131 Roma, Italy.; Space Research Organization in the Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, Netherlands), AM(Istituto Fisica Cosmica e Applicazioni all'Informatica, C.N.R., Via U. La Malfa 153, 90146 Palermo, Italy), AN(Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, 40129 Bologna, Italy), AO(Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, 40129 Bologna, Italy), AP(Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, 40129 Bologna, Italy), AQ(Istituto Astrofisica Spaziale, C.N.R., Via Fosso del Cavaliere, 00133 Roma, Italy), AR(Istituto Astrofisica Spaziale, C.N.R., Via Fosso del Cavaliere, 00133 Roma, Italy), AS(BeppoSAX Operative Control Center, Via Corcolle 19, 00131 Roma, Italy), AT(Space Research Organization in the Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, Netherlands), AU(National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801), AV(Palomar Observatory 105-24, Caltech, Pasadena, CA 91125), AW(Dipartimento di Fisica, Università Roma Tre, Via della Vasca Navale, 84, 00146 Roma, Italy)
Journal:
The Astrophysical Journal, Volume 540, Issue 2, pp. 697-703. (ApJ Homepage)
Publication Date:
09/2000
Origin:
UCP
ApJ Keywords:
Gamma Rays: Bursts, Gamma Rays: Observations, Shock Waves, X-Rays: General
Abstract Copyright:
(c) 2000: The American Astronomical Society
Bibliographic Code:
2000ApJ...540..697F

Abstract

We discuss observations of the prompt X- and γ-ray emission and X-ray afterglow from GRB 981226. This event has the weakest gamma-ray peak flux detected with the BeppoSAX Gamma-Ray Burst Monitor. It shows an isolated X-ray precursor and the highest X-ray to gamma-ray fluence ratio measured thus far with the BeppoSAX Wide Field Cameras. The event was followed up with the BeppoSAX Narrow Field Instruments, and the X-ray afterglow was detected up to 10 keV. The afterglow flux is observed to rise from a level below the sensitivity of the MECS/LECS telescopes up to a peak flux of (5+/-1)×10-13 ergs cm-2 s-1 in the 2-10 keV energy band. This rise is followed by a decline according to a power law with an index of 1.31+0.44-0.39. We discuss these results in the light of the current GRB models.

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Title:
BEPPOSAX Observations of GRB 980425: Detection of the Prompt Event and Monitoring of the Error Box
Authors:
Pian, E.; Amati, L.; Antonelli, L. A.; Butler, R. C.; Costa, E.; Cusumano, G.; Danziger, J.; Feroci, M.; Fiore, F.; Frontera, F.; Giommi, P.; Masetti, N.; Muller, J. M.; Nicastro, L.; Oosterbroek, T.; Orlandini, M.; Owens, A.; Palazzi, E.; Parmar, A.; Piro, L.; in't Zand, J. J. M.; Castro-Tirado, A.; Coletta, A.; Dal Fiume, D.; Del Sordo, S.; Heise, J.; Soffitta, P.; Torroni, V.
Affiliation:
AA(Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri, Consiglio Nazionale delle Ricerche, Via Gobetti 101, I-40129 Bologna, Italy), AB(Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri, Consiglio Nazionale delle Ricerche, Via Gobetti 101, I-40129 Bologna, Italy), AC(Osservatorio Astronomico di Roma, sede di Monteporzio Catone, Via Frascati 33, I-00040 Monteporzio Catone, Italy), AD(Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri, Consiglio Nazionale delle Ricerche, Via Gobetti 101, I-40129 Bologna, Italy), AE(Istituto di Astrofisica Spaziale, Consiglio Nazionale delle Ricerche, Via Fosso del Cavaliere, Area della Ricerca di Tor Vergata, I-00131 Rome, Italy), AF(Istituto di Fisica Cosmica e Applicazioni dell'Informatica, Via Ugo La Malfa 153, I-90146 Palermo, Italy), AG(Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, I-34131 Trieste, Italy), AH(Istituto di Astrofisica Spaziale, Consiglio Nazionale delle Ricerche, Via Fosso del Cavaliere, Area della Ricerca di Tor Vergata, I-00131 Rome, Italy), AI(BeppoSAX Scientific Data Center, Via Corcolle 19, I-00131 Rome, Italy), AJ(Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri, Consiglio Nazionale delle Ricerche, Via Gobetti 101, I-40129 Bologna, Italy.; Physics Department, University of Ferrara, Via Paradiso, 12, I-44100 Ferrara, Italy), AK(BeppoSAX Scientific Data Center, Via Corcolle 19, I-00131 Rome, Italy), AL(Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri, Consiglio Nazionale delle Ricerche, Via Gobetti 101, I-40129 Bologna, Italy), AM(BeppoSAX Scientific Data Center, Via Corcolle 19, I-00131 Rome, Italy), AN(Istituto di Fisica Cosmica e Applicazioni dell'Informatica, Via Ugo La Malfa 153, I-90146 Palermo, Italy), AO(Astrophysics Division, Space Science Department of European Space Agency, European Space Research and Technology Centre, P.O. Box 299, 2200 AG Noordwijk, The Netherlands), AP(Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri, Consiglio Nazionale delle Ricerche, Via Gobetti 101, I-40129 Bologna, Italy), AQ(Astrophysics Division, Space Science Department of European Space Agency, European Space Research and Technology Centre, P.O. Box 299, 2200 AG Noordwijk, The Netherlands), AR(Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri, Consiglio Nazionale delle Ricerche, Via Gobetti 101, I-40129 Bologna, Italy), AS(Astrophysics Division, Space Science Department of European Space Agency, European Space Research and Technology Centre, P.O. Box 299, 2200 AG Noordwijk, The Netherlands), AT(Istituto di Astrofisica Spaziale, Consiglio Nazionale delle Ricerche, Via Fosso del Cavaliere, Area della Ricerca di Tor Vergata, I-00131 Rome, Italy), AU(Space Research Organization Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands), AV(Instituto de Astrofisico de Andalucía Consejo Superior de Investigaciones Científicas, Granada, Spain and Laboratorio de Astrofísica Espacial y Física Fundamental, Instituto Nacional de Técnica Aerospacial, Madrid, Spain), AW(BeppoSAX Scientific Data Center, Via Corcolle 19, I-00131 Rome, Italy), AX(Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri, Consiglio Nazionale delle Ricerche, Via Gobetti 101, I-40129 Bologna, Italy), AY(Istituto di Fisica Cosmica e Applicazioni dell'Informatica, Via Ugo La Malfa 153, I-90146 Palermo, Italy), AZ(Space Research Organization Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands), BA(Istituto di Astrofisica Spaziale, Consiglio Nazionale delle Ricerche, Via Fosso del Cavaliere, Area della Ricerca di Tor Vergata, I-00131 Rome, Italy), BB(BeppoSAX Scientific Data Center, Via Corcolle 19, I-00131 Rome, Italy)
Journal:
The Astrophysical Journal, Volume 536, Issue 2, pp. 778-787. (ApJ Homepage)
Publication Date:
06/2000
Origin:
UCP
ApJ Keywords:
Gamma Rays: Bursts, Stars: Supernovae: Individual: Alphanumeric: SN 1998bw
Abstract Copyright:
(c) 2000: The American Astronomical Society
Bibliographic Code:
2000ApJ...536..778P

Abstract

We present BeppoSAX follow-up observations of GRB 980425 obtained with the Narrow Field Instruments (NFI) in 1998 April, May, and November. The first NFI observation has detected within the 8' radius error box of the gamma-ray burst (GRB) an X-ray source positionally consistent with the supernova 1998bw, which exploded within a day of GRB 980425, and a fainter X-ray source, not consistent with the position of the supernova. The former source is detected in the following NFI pointings and exhibits a decline of a factor of 2 in six months. If it is associated with SN 1998bw, this is the first detection of X-ray emission from a Type I supernova above 2 keV. The latter source exhibits only marginally significant variability. The X-ray spectra and variability of the supernova are compared with thermal and nonthermal models of supernova high-energy emission. Based on the BeppoSAX data, it is not possible to establish firmly which of the two detected sources is the GRB X-ray counterpart, although probability considerations favor the supernova.

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Title:
The WGACAT version of ROSAT sources (White+ 2000)
Authors:
White, N. E.; Giommi, P.; Angelini, L.
Journal:
VizieR On-line Data Catalog: IX/31. Originally published in: Laboratory for High Energy Astrophysics (LHEA/NASA), Greenbelt (2000)
Publication Date:
06/2000
Origin:
SIMBAD
Keywords:
X-ray sources, Cross identifications
Bibliographic Code:
2000yCat.9031....0W

Abstract

WGACAT is a point source catalogue generated from all ROSAT PSPC (Position Sensitive Proportional Counter) pointed observations. This catalog has been generated by N.E. White (HEASARC/GSFC), P. Giommi (SDC/ASI) and L. Angelini (HEASARC/GSFC) and is a private research effort, not related to the official catalogs generated by the ROSAT project. The WGACAT was made first publicly available in November 1994 through the HEASARC on-line service (White, Giommi and Angelini 1994), with a first minor revision in March 1995 (WGACAT95). It was generated using all the public ROSAT PSPC pointed data available than, corresponding to 75% of the entire set, and featured ~ 68000 detections of which 62000 were unique sources. The current version, released in May 2000, is the final and complete version of WGACAT and includes the remaining sequences not processed in the WGACAT95. WGACAT (May 2000) contains about 88,000 detections, with more than 84,000 individual sources, obtained from 4160 sequences. The catalog was generated using an optimized sliding cell detect algorithm in XIMAGE (first developed for the EXOSAT project). The inner and outer parts of the images were run separately, to maximize the sensitivity to source detection. This method is very sensitive in finding point sources, but can also find spurious sources where there is extended emission. We have visually inspected each detection, removed the obvious spurious cases and assigned a quality flag to each detection. (2 data files).

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Title:
An update to the WGACAT ROSAT PSPC source catalog
Authors:
Angelini, L.; Park, S.; White, N. E.; Giommi, P.
Affiliation:
AA(LHEA/GSFC/USRA), AB(LHEA/GSFC/USRA), AC(LHEA/GSFC), AD(BeppoSAX-SDC/ASI)
Journal:
American Astronomical Society Meeting 196, #53.10
Publication Date:
05/2000
Origin:
AAS
Abstract Copyright:
(c) 2000: American Astronomical Society
Bibliographic Code:
2000AAS...196.5310A

Abstract

We present an updated and the final version of the WGACAT generated using all the PSPC ROSAT public pointed observation in the HEASARC archive. The large 2 degree field of view of the ROSAT PSPC makes it ideal as a survey instrument. Over the entire 4 yr pointed phase of the ROSAT program approximately 18% of the sky has been covered to varying degrees of sensitivity. While the sky coverage is not complete, each observation has an exposure typically a factor of 100 longer than that achieved during the six month ROSAT all sky survey. The first version of the WGACAT was released in November 1994 with an update in March 1995, and it included data that were available in the public archive as of Feb. 1995. The catalog contained an excess of 68,000 point sources. The updated version, presented here, includes all the data taken with the ROSAT PSPC during the pointed phase and contains ~ 88000 sources. The catalog has been quality checked and for each source a number of useful parameters have been added. For each observation intensity, energy and timing images are available and for each source detected a spectrum and lightcurve. The catalog and the data products can be accessed via the HEASARC on-line service (http://heasarc.gsfc.nasa.gov) or from the wgacat home page (http://wgacat.gsfc.nasa.gov).

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Title:
BeppoSAX spectrum of GRB971214: evidence of a substantial energy output during afterglow
Authors:
Dal Fiume, D.; Amati, L.; Antonelli, L. A.; Fiore, F.; Muller, J. M.; Parmar, A.; Masetti, N.; Pian, E.; Costa, E.; Frontera, F.; Piro, L.; Heise, J.; Butler, R. C.; Coletta, A.; Feroci, M.; Giommi, P.; Nicastro, L.; Orlandini, M.; Palazzi, E.; Pizzichini, G.; Tavani, M.
Affiliation:
AA( Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri (TeSRE), C.N.R., via Gobetti 101, 40129 Bologna, Italy), AB( Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri (TeSRE), C.N.R., via Gobetti 101, 40129 Bologna, Italy), AC(Beppo-SAX Scientific Data Center, Via Corcolle 19, 00131 Roma, Italy; Osservatorio Astronomico di Roma, Via Frascati 33, 00044 Roma, Italy), AD(Beppo-SAX Scientific Data Center, Via Corcolle 19, 00131 Roma, Italy; Osservatorio Astronomico di Roma, Via Frascati 33, 00044 Roma, Italy), AE(Beppo-SAX Scientific Data Center, Via Corcolle 19, 00131 Roma, Italy; Space Research Organization Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands), AF(Astrophysics Division, Space Science Department of ESA, ESTEC, P.O. Box 299, 2200 AG Noordwijk, The Netherlands), AG( Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri (TeSRE), C.N.R., via Gobetti 101, 40129 Bologna, Italy), AH( Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri (TeSRE), C.N.R., via Gobetti 101, 40129 Bologna, Italy), AI(Istituto di Astrofisica Spaziale (IAS), C.N.R., Via Fosso del Cavaliere, 00133 Roma, Italy), AJ( Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri (TeSRE), C.N.R., via Gobetti 101, 40129 Bologna, Italy; Dipartimento di Fisica, Universitàdi Ferrara, Via Paradiso 12, 44100 Ferrara, Italy), AK(Istituto di Astrofisica Spaziale (IAS), C.N.R., Via Fosso del Cavaliere, 00133 Roma, Italy), AL(Space Research Organization Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands), AM(Agenzia Spaziale Italiana, Viale Regina Margherita 202, 00198 Roma, Italy), AN(Osservatorio Astronomico di Roma, Via Frascati 33, 00044 Roma, Italy), AO(Istituto di Astrofisica Spaziale (IAS), C.N.R., Via Fosso del Cavaliere, 00133 Roma, Italy), AP(Beppo-SAX Scientific Data Center, Via Corcolle 19, 00131 Roma, Italy), AQ(Istituto di Fisica Cosmica con Applicazioni all'Informatica (IFCAI), C.N.R., Via U. La Malfa 153, 90139, Palermo, Italy), AR( Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri (TeSRE), C.N.R., via Gobetti 101, 40129 Bologna, Italy), AS( Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri (TeSRE), C.N.R., via Gobetti 101, 40129 Bologna, Italy), AT( Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri (TeSRE), C.N.R., via Gobetti 101, 40129 Bologna, Italy), AU(Istituto di Fisica Cosmica ``G. P. S. Occhialini'', C.N.R., via Bassini 15, 20133 Milano, Italy)
Journal:
Astronomy and Astrophysics, v.355, p.454-460 (2000) (A&A Homepage)
Publication Date:
03/2000
Origin:
A&A
A&A Keywords:
GAMMA RAYS: BURSTS, GAMMA RAYS: OBSERVATIONS, X-RAYS: GENERAL
Abstract Copyright:
(c) 2000: Astronomy & Astrophysics
Bibliographic Code:
2000A&A...355..454D

Abstract

We report the X/gamma -ray spectrum of GRB971214 and of its afterglow. The afterglow was measured few hours after the main event and for an elapsed time of more than two days. The measure of this GRB and afterglow is relevant due to its extreme, cosmological distance (z=3.42). The prompt event shows a hard photon spectrum, consistent with a broken power law with photon indices Gamma_X ~0.1 below ~ 20 keV and Gamma_ gamma ~1.3 above 60 keV. The afterglow spectrum, measured with the MECS and LECS BeppoSAX telescopes, is consistent with a power law with spectral photon index Gamma =1.6. Within the statistical accuracy of our measure no spectral evolution is detected during the observation of the afterglow. When integrated during the time span covered by BeppoSAX observations, the power in the afterglow emission, even with very conservative assumptions, is at least comparable with the power in the main event. The IR-to-X rays broad band spectrum is also presented, collecting data from the literature and adding them to the BeppoSAX measure. It shows that the predictions from synchrotron emission models is qualitatively confirmed. The BeppoSAX measurement of the X and gamma ray spectrum of this GRB/afterglow is discussed in the framework of current theoretical models

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Title:
The 0.1-100keV spectrum and variability of Mrk 421 in a high state
Authors:
Malizia, A.; Capalbi, M.; Fiore, F.; Giommi, P.; Gandolfi, G.; Tesseri, A.; Antonelli, L. A.; Butler, R. C.; Celidonio, G.; Coletta, A.; Di Ciolo, L.; Muller, J. M.; Piro, L.; Rebecchi, S.; Ricci, D.; Ricci, R.; Smith, M.; Torroni, V.
Affiliation:
AA(), AB(BeppoSAX Science Data Center, Via Corcolle 19, I-00131 Roma, Italy; Telespazio, Via Corcolle 19, I-00131 Roma, Italy), AC(BeppoSAX Science Data Center, Via Corcolle 19, I-00131 Roma, Italy; Osservatorio Astronomico di Roma, Via dell'Osservatorio, I-00044 Monteporzio Catone, Italy), AD(BeppoSAX Science Data Center, Via Corcolle 19, I-00131 Roma, Italy; ASI, Area Ricerca Scientifica, Roma, Italy), AE(Telespazio, Via Corcolle 19, I-00131 Roma, Italy; BeppoSAX SOC, Via Corcolle 19, I-00131 Roma, Italy), AF(Telespazio, Via Corcolle 19, I-00131 Roma, Italy; BeppoSAX SOC, Via Corcolle 19, I-00131 Roma, Italy), AG(BeppoSAX Science Data Center, Via Corcolle 19, I-00131 Roma, Italy; Osservatorio Astronomico di Roma, Via dell'Osservatorio, I-00044 Monteporzio Catone, Italy), AH(ASI, Area Ricerca Scientifica, Roma, Italy), AI(Telespazio, Via Corcolle 19, I-00131 Roma, Italy; BeppoSAX SOC, Via Corcolle 19, I-00131 Roma, Italy), AJ(Telespazio, Via Corcolle 19, I-00131 Roma, Italy; BeppoSAX SOC, Via Corcolle 19, I-00131 Roma, Italy), AK(Telespazio, Via Corcolle 19, I-00131 Roma, Italy; BeppoSAX SOC, Via Corcolle 19, I-00131 Roma, Italy), AL(BeppoSAX SOC, Via Corcolle 19, I-00131 Roma, Italy; SRON, Sorbonnelaan 2, 3584 CA Ultrecht, the Netherlands), AM(Istituto di Astrofisica Spaziale, CNR, Via Fosso Del Cavalire, I-00133, Roma, Italy), AN(Telespazio, Via Corcolle 19, I-00131 Roma, Italy; BeppoSAX SOC, Via Corcolle 19, I-00131 Roma, Italy), AO(Telespazio, Via Corcolle 19, I-00131 Roma, Italy; BeppoSAX SOC, Via Corcolle 19, I-00131 Roma, Italy), AP(Telespazio, Via Corcolle 19, I-00131 Roma, Italy; BeppoSAX SOC, Via Corcolle 19, I-00131 Roma, Italy), AQ(BeppoSAX SOC, Via Corcolle 19, I-00131 Roma, Italy; SRON, Sorbonnelaan 2, 3584 CA Ultrecht, the Netherlands), AR(Telespazio, Via Corcolle 19, I-00131 Roma, Italy; BeppoSAX SOC, Via Corcolle 19, I-00131 Roma, Italy)
Journal:
Monthly Notices of the Royal Astronomical Society, Volume 312, Issue 1, pp. 123-129. (MNRAS Homepage)
Publication Date:
02/2000
Origin:
MNRAS
MNRAS Keywords:
GALAXIES: ACTIVE, BL LACERTAE OBJECTS: INDIVIDUAL: MRK 421, X-RAYS: GALAXIES
Abstract Copyright:
(c) 2000 The Royal Astronomical Society
Bibliographic Code:
2000MNRAS.312..123M

Abstract

The results of a BeppoSAX target of opportunity (TOO) observation of the BL Lac object Mrk 421 during a high-intensity state are reported and compared with monitoring X-ray data collected with the BeppoSAX Wide Field Cameras (WFC) and the RXTE All Sky Monitor (ASM). The 0.1-100keV spectrum of Mrk 421 shows continuous convex curvature that can be interpreted as the high-energy end of the synchrotron emission. The source shows significant short-term temporal and spectral variability, which can be interpreted in terms of synchrotron cooling. The comparison of our results with those of previous observations when the source was a factor 3-5 fainter shows evidence for strong spectral variability, with the maximum of the synchrotron power shifting to higher energy during high states. This behaviour suggests an increase in the number of energetic electrons during high states.

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Title:
The concave X-ray spectrum of the blazar ON 231: the signature of intermediate BL Lacertae objects
Authors:
Tagliaferri, G.; Ghisellini, G.; Giommi, P.; Chiappetti, L.; Maraschi, L.; Celotti, A.; Chiaberge, M.; Fossati, G.; Massaro, E.; Maesano, M.; Montagni, F.; Nesci, R.; Nucciarelli, G.; Pian, E.; Raiteri, C. M.; Tavecchio, F.; Tosti, G.; Treves, A.; Villata, M.; Wolter, A.
Affiliation:
AA(Osservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, Italy), AB(Osservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, Italy), AC(BeppoSAX Science Data Center, ASI, Via Corcolle 19, 00131 Roma, Italy), AD(Istituto di Fisica Cosmica G.Occhialini, CNR, Via Bassini 15, 20133 Milano, Italy), AE(Osservatorio Astronomico di Brera, Via Brera 28, 20121 Milano, Italy), AF(SISSA/ISAS, Via Beirut 2-4, 34014 Trieste, Italy), AG(SISSA/ISAS, Via Beirut 2-4, 34014 Trieste, Italy), AH(CASS, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424, USA), AI(Istituto Astronomico, Università``La Sapienza'', Via Lancisi 29, 00161 Roma, Italy), AJ(Istituto Astronomico, Università``La Sapienza'', Via Lancisi 29, 00161 Roma, Italy), AK(Istituto Astronomico, Università``La Sapienza'', Via Lancisi 29, 00161 Roma, Italy), AL(Istituto Astronomico, Università``La Sapienza'', Via Lancisi 29, 00161 Roma, Italy), AM(Osservatorio Astronomico, Universitàdi Perugia, Via A. Pascoli, 06100 Perugia, Italy), AN(ITeSRE/CNR, Via Gobetti 101, 40129 Bologna, Italy), AO(Osservatorio Astronomico di Torino, Strada Osservatorio 20, 10025 Pino Torinese, Italy), AP(Osservatorio Astronomico di Brera, Via Brera 28, 20121 Milano, Italy), AQ(Osservatorio Astronomico, Universitàdi Perugia, Via A. Pascoli, 06100 Perugia, Italy), AR(Istituto di Fisica, Universitàdell'Insubria, Via Lucini 3, 22100 Como, Italy), AS(Osservatorio Astronomico di Torino, Strada Osservatorio 20, 10025 Pino Torinese, Italy), AT(Osservatorio Astronomico di Brera, Via Brera 28, 20121 Milano, Italy)
Journal:
Astronomy and Astrophysics, v.354, p.431-438 (2000) (A&A Homepage)
Publication Date:
02/2000
Origin:
A&A
A&A Keywords:
GALAXIES: BL LACERTAE OBJECTS: GENERAL, GALAXIES: BL LACERTAE OBJECTS: INDIVIDUAL: ON 231, X-RAYS: GALAXIES
Abstract Copyright:
(c) 2000: Astronomy & Astrophysics
Bibliographic Code:
2000A&A...354..431T

Abstract

ON 231 was observed with BeppoSAX in May and June 1998, following an exceptional optical outburst which occured in April-May. We measured the X-ray spectrum from 0.1 up to 100 keV. In both occasions the spectrum had a concave shape, with a break detected at about 4 and 2.5 keV, respectively. We interpret the steeper component at energies below the break as due to synchrotron emission and the extremely flat component at energies above the break as due to inverse Compton emission. This is so far the best example in which both the synchrotron and the Inverse Compton component are detected simultaneously and with the same instruments in the X-ray spectrum of a blazar. We detect a decrease of the X-ray flux of about 30% below the break between the first and the second observation, and smaller variability amplitude between 4 and 10 keV. During the May observation we also detected a fast variability event with the flux below 4 keV increasing by about a factor of three in 5 hours. Above 4 keV no variability was detected. We discuss these results in the framework of synchrotron self-Compton models

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Title:
The BeppoSAX view of the hard X-ray background
Authors:
Comastri, A.; Fiore, F.; Giommi, P.; La Franca, F.; Elvis, M.; Matt, G.; Molendi, S.; Perola, G. C.
Affiliation:
AA(Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna, Italy), AB(), AC(SAX Science Data Center c/o Nuova Telespazio, via Corcolle 19, I-00131, Roma, Italy), AD(Dipartimento di Fisica Università ``Roma Tre'', via della Vasca Navale 84, I-00146, Roma, Italy), AE(Harvard Smithsonian Center for Astrophysics, 60 Garden street, MA-02138, Cambridge, USA), AF(Dipartimento di Fisica Università ``Roma Tre'', via della Vasca Navale 84, I-00146, Roma, Italy), AG(Istituto di Fisica Cosmica e Tecnologie Relative - CNR, via Bassini 15, I-20133, Milano, Italy), AH(Dipartimento di Fisica Università ``Roma Tre'', via della Vasca Navale 84, I-00146, Roma, Italy)
Journal:
Advances in Space Research, Volume 25, Issue 3-4, p. 833-838. (AdSpR Homepage)
Publication Date:
00/2000
Origin:
ELSEVIER
Abstract Copyright:
(c) 2000 Elsevier Science B.V. All rights reserved.
Bibliographic Code:
2000AdSpR..25..833C

Abstract

First results on a medium-deep X-ray survey in the ``new'' 5-10 keV band carried out with the MECS detectors onboard BeppoSAX are presented. The High Energy Llarge Area Survey (HELLAS) is aimed to directly explore a band where the energy density of the X-ray background is more than twice than that in the soft (0.5-2.0 keV) band. The optical identification follow-up of the first ten HELLAS hard X-ray sources indicate that Active Galactic Nuclei are the dominant population at 5-10 keV fluxes of the order of 10-13 erg cm-2 s-1. We discuss the implications of these findings for the AGN synthesis models for the XRB

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Title:
GRB 001109 X-ray afterglow with BeppoSAX.
Authors:
Amati, L.; Frontera, F.; Pian, E.; Giommi, P.; Capalbi, M.; Costa, E.; Gandolfi, G.; in't Zand, J. J. M.; Guidorzi, C.; Granata, S.; Paolino, A.
Journal:
GRB Circular Network, 885, 1 (2000)
Publication Date:
00/2000
Origin:
SIMBAD
Bibliographic Code:
2000GCN...885....1A

Abstract

Not Available

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Title:
BeppoSAX Observations of the Radio Galaxy Centaurus A
Authors:
Grandi, P.; Urry, C. M.; Maraschi, L.; Guainazzi, M.; Massaro, E.; Matt, G.; Bassani, L.; Cinematti, A.; Giommi, P.; Dadina, M.; Perola, G. C.; Piro, L.; Santangelo, A.
Affiliation:
AA(IAS/CNR, Area di Ricerca Tor Vergata, Via Fosso del Cavaliere, I-00133 Roma, Italy), AB(STScI, 3700 San Martin Drive, Baltimore, MD 21218, USA), AC(Osservatorio Astronomico di Brera, Via Brera 28, I-20121 Milano, Italy), AD(SSD/ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands), AE(Istituto Astronomico di Roma, Via Lancisi 29 Roma, Italy), AF(Università degli Studi ``Roma 3'', Via della Vasca Navale 84, I-00146 Roma, Italy), AG(ITESRE/CNR, Via P. Gobetti 101, I-40129, Bologna, Italy), AH(Osservatorio Astronomico di Arcetri, Largo E. Fermi 5, I-50125, Firenze, Italy), AI(BeppoSAX SDC, c/o Nuova Telespazio, Via Corcolle 19, I-90146, Roma, Italy), AJ(BeppoSAX SDC, c/o Nuova Telespazio, Via Corcolle 19, I-90146, Roma, Italy), AK(Università degli Studi ``Roma 3'', Via della Vasca Navale 84, I-00146 Roma, Italy), AL(IAS/CNR, Area di Ricerca Tor Vergata, Via Fosso del Cavaliere, I-00133 Roma, Italy), AM(IFCAI/CNR, Via U. La Malfa 153, I-90146, Palermo, Italy)
Journal:
Advances in Space Research, Volume 25, Issue 3-4, p. 485-488. (AdSpR Homepage)
Publication Date:
00/2000
Origin:
ELSEVIER
Abstract Copyright:
(c) 2000 Elsevier Science B.V. All rights reserved.
Bibliographic Code:
2000AdSpR..25..485G

Abstract

We present preliminary results from two observations of the radio galaxy Centaurus A performed by the BeppoSAX satellite on 1997 February 20-21 and on 1998 January 6-7. In the second pointing the source was brighter by a factor 1.3. We did not detect any spectral variation of the nuclear continuum in spite of the long-term flux change between the two observations. At both epochs, the nuclear point-like emission was well fitted with a strongly absorbed (NH ~ 1023 cm-2) power law with an exponential cutoff at high energies (Ecut > 200 keV). We also observed a significant flux variation of the iron line between the two observations. The flux of the line and of the continuum changed in the opposite sense. The line is more intense at the first epoch, when the nuclear source was at the lower intensity level. The implied delay between the continuum and line variations strongly suggests that the cold material responsible for the iron line production is not located very near to the primary X-ray source. There is also evidence that the line profile changed between the two epochs, being broader and slightly blueshifted when the source was fainter. It is possible that the emission feature is a blend of cold and ionized iron lines produced in separate regions surrounding the nuclear source

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Title:
BeppoSAX observations of the BL Lac object 1E1207.9+3945
Authors:
Cusumano, G.; Mineo, T.; Giommi, P.
Affiliation:
AA(IFCAI-CNR, Palermo, Italy), AB(IFCAI-CNR, Palermo, Italy), AC(BeppoSAX SDC, ASI, Roma, Italy )
Journal:
BLAZAR Data, Vol. 2, n. 2 (2000)
Publication Date:
00/2000
Origin:
BLAZ
Bibliographic Code:
2000BlazD...2....2V

Abstract

We present the results of four X-ray observations of the BL Lac object 1E1207.9+3945 performed in 1996 with the MECS instrument onboard BeppoSAX. The source shows an unabsorbed flux in 2-10 keV range of (3.39 +/- 0.08) x 10-12 erg s-1 cm-2 with a photon spectral index of 2.12 +/- 0.06. No temporal variations during BeppoSAX observation have been detected. From the comparison with previous PSPC and EXOSAT observations, a secular variation in the 2-10 keV flux has been revealed.

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Title:
Broad Band Properties of Radio-Loud Emission Line AGNs
Authors:
Grandi, P.; Palumbo, G. G. C.; Giommi, P.; Malaguti, G.; Maraschi, L.; Urry, C. M.; Piconcelli, E.
Journal:
The Fifth Compton Symposium, Proceedings of the fifth Compton Symposium, held in Portsmouth, NH, USA, September 1999. Melville, NY: American Institute of Physics (AIP), 2000. Edited by Mark L. McConnell and James M. Ryan AIP Conference Proceedings, Vol. 510., p.382 (CoMP Homepage)
Publication Date:
00/2000
Origin:
ADS
Bibliographic Code:
2000comp.symp..382G

Abstract

Not Available

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Title:
The BeppoSAX View of the Hard X-Ray Background
Authors:
Comastri, A.; Fiore, F.; Giommi, P.; La Franca, F.; Elvis, M.; Matt, G.; Molendi, S.; Perola, G. C.
Journal:
Broad Band X-ray Spectra of Cosmic Sources, Proceedings of the E1.1 Symposium of COSPAR Scientific Commission E, held during the 32nd COSPAR Scientific Assembly, 12-19 July, 1998 in Nagoya, Japan. Edited by K. Makishima, L. Piro, and T. Takahashi. Published for the Committee on Space Research by Pergamon Press, 2000., p.833
Publication Date:
00/2000
Origin:
ADS
Bibliographic Code:
2000bbxs.conf..833C

Abstract

Not Available

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Title:
The Deep X-ray Radio Blazar Survey (DXRBS)
Authors:
Padovani, P.; Landt, H.; Perlman, E.; Giommi, P.
Affiliation:
AA(ESA, STScI), AB(STScI), AC(STScI), AD(BeppoSAX SDC)
Journal:
American Astronomical Society, 195th AAS Meeting, #16.03; Bulletin of the American Astronomical Society, Vol. 31, p.1396
Publication Date:
12/1999
Origin:
AAS
Abstract Copyright:
(c) 1999: American Astronomical Society
Bibliographic Code:
1999AAS...195.1603P

Abstract

We give an update on the status of the Deep X-ray Radio Blazar Survey (DXRBS). The DXRBS candidate list is obtained by correlating the ROSAT WGACAT database with several radio catalogs and restricting the selection to flat spectrum radio sources (α r <= 0.70). The selection criteria result in a very high efficiency ( 90%) at finding blazars, that is flat-spectrum radio quasars (FSRQ) and BL Lacertae objects. DXRBS will provide a sample of about 350 blazars, selected in an homogeneous way and reaching X-ray and radio fluxes about 10 -- 20 times deeper than currently available, complete blazar samples. Identification of the sources is 85% complete. We present here some DXRBS results as of December 1999, namely: a breakdown of the source classification; the redshift and luminosity distribution for FSRQ and BL Lacs; the number counts for both classes, which for the first time reach relatively faint flux levels ( 50 mJy and 2 x 10-14 c.g.s. for the radio and X-ray band respectively); and an estimate of the evolutionary properties of DXRBS blazars.

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Title:
The sedentary multifrequency survey - I. Statistical identification and cosmological properties of high-energy peaked BL Lacs
Authors:
Giommi, P.; Menna, M. T.; Padovani, P.
Affiliation:
AA(BeppoSAX Science Data Center, ASI, Via Corcolle, 19 I-00131 Roma, Italy; Area per la Ricerca Scientifica, Italian Space Agency (ASI), via di Villa Patrizi 13, 00161 Roma, Italy), AB(BeppoSAX Science Data Center, ASI, Via Corcolle, 19 I-00131 Roma, Italy), AC(Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA)
Journal:
Monthly Notices, Volume 310, Issue 2, pp. 465-475. (MNRAS Homepage)
Publication Date:
12/1999
Origin:
MNRAS
MNRAS Keywords:
GALAXIES: ACTIVE, BL LACERTAE OBJECTS: GENERAL
Abstract Copyright:
(c) 1999 The Royal Astronomical Society
Bibliographic Code:
1999MNRAS.310..465G

Abstract

We have assembled a multifrequency data base by cross-correlating the NRAO VLA Sky Survey (NVSS) catalogue of radio sources with the RASSBSC list of soft X-ray sources, obtaining optical magnitude estimates from the Palomar and UK Schmidt surveys as provided by the Automated Plate Measurement (APM) and COSMOS on-line services. By exploiting the nearly unique broad-band properties of high-energy peaked BL Lacs (HBL), we have statistically identified a sample of 218 objects that is expected to include about 85per cent of BL Lacs and that is therefore several times larger than all other published samples of HBLs. Using a subset (155 objects) that is radio-flux-limited and statistically well-defined, we have derived the VVm distribution and the logN-logS of extreme HBLs (fxfr>=3x10-10ergcm- 2s-1Jy-1) down to 3.5mJy. We find that the logN-logS flattens around 20mJy and that <VVm>=0.42+/-0.02. This extends to the radio band earlier results, based on much smaller X-ray-selected samples, about the anomalous cosmological observational properties of HBLs. A comparison with the expected radio logN-logS of all BL Lacs (based on a beaming model) shows that extreme HBLs make up roughly 2per cent of the BL Lac population, independently of radio flux. This result, together with the flatness of the radio logN-logS at low fluxes, is in contrast with the predictions of a recent model that assumes an anticorrelation between peak frequency and bolometric luminosity. This scenario would in fact result in an increasing dominance of HBLs at lower radio fluxes; an effect that, if at all present, must start at fluxes fainter than our survey limit. The extreme fxfr flux ratios and high X-ray fluxes of these BL Lacs makes them good candidate TeV sources; some of the brighter (and closer) ones are possibly detectable with the current generation of Cerenkov telescopes. Statistical identification of sources based on their location in multiparameter space, of the kind described here, will have to become commonplace with the advent of the many large, deep surveys at various frequencies currently scheduled or under construction.

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Title:
Synchrotron and inverse Compton variability in the BL Lacertae object S5 0716+714
Authors:
Giommi, P.; Massaro, E.; Chiappetti, L.; Ferrara, E. C.; Ghisellini, G.; Jang, Minhwan; Maesano, M.; Miller, H. R.; Montagni, F.; Nesci, R.; Padovani, P.; Perlman, E.; Raiteri, C. M.; Sclavi, S.; Tagliaferri, G.; Tosti, G.; Villata, M.
Affiliation:
AA(BeppoSAX Science Data Center, ASI, Via Corcolle 19, 00131 Roma, Italy), AB(Istituto Astronomico, Universita' ``La Sapienza", Via Lancisi 29 00161 Roma, Italy), AC(IFC, CNR, Via Bassini 15, Milan, Italy), AD(Department of Physics and Astronomy, Georgia State University Atlanta, GA 30303, USA), AE(Osservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, Italy), AF(Department Astronomy and Space Science, Kyung Hee University, Yongin, Kyungki-Do 449-701, Korea), AG(Istituto Astronomico, Universita' ``La Sapienza", Via Lancisi 29 00161 Roma, Italy), AH(Department of Physics and Astronomy, Georgia State University Atlanta, GA 30303, USA), AI(Istituto Astronomico, Universita' ``La Sapienza", Via Lancisi 29 00161 Roma, Italy), AJ(Istituto Astronomico, Universita' ``La Sapienza", Via Lancisi 29 00161 Roma, Italy), AK(Space Telescope Science Institute 3700 San Martin Drive, Baltimore, MD 21218, USA), AL(Space Telescope Science Institute 3700 San Martin Drive, Baltimore, MD 21218, USA), AM(Osservatorio Astronomico di Torino, Strada Osservatorio 20 10025 Pino Torinese, Italy), AN(Istituto Astronomico, Universita' ``La Sapienza", Via Lancisi 29 00161 Roma, Italy), AO(Osservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, Italy), AP(Osservatorio Astronomico, Universita' di Perugia, Perugia, Italy), AQ(Osservatorio Astronomico di Torino, Strada Osservatorio 20 10025 Pino Torinese, Italy)
Journal:
Astronomy and Astrophysics, v.351, p.59-64 (1999) (A&A Homepage)
Publication Date:
11/1999
Origin:
A&A
A&A Keywords:
RADIATION MECHANISMS: NON-THERMAL, GALAXIES: ACTIVE, GALAXIES: BL LACERTAE OBJECTS: INDIVIDUAL: S5 0716+714, X-RAYS: GALAXIES
Abstract Copyright:
(c) 1999: Astronomy & Astrophysics
Bibliographic Code:
1999A&A...351...59G

Abstract

We report intensity variations of different spectral components in the BL Lac object S5 0716+714 detected during coordinated BeppoSAX and optical observations in 1996 and 1998. The transition between synchrotron and inverse Compton emission has been clearly detected as sharp X-ray spectral breaks at around 2-3 keV on both occasions. Correlated optical and soft X-ray variability was found during the second {BeppoSAX} pointing when intensive optical monitoring could be arranged. The hard (Compton) component changed by a factor of 2 between the two observations, but remained stable within each exposure. During events of rapid variability S5 0716+714 showed spectral steepening with intensity, a behaviour rarely observed in BL Lacs. We interpret these findings as the probable consequence of a shift of the synchrotron peak emission from the IR/optical band to higher energies, causing the synchrotron tail to push into the soft X-ray band more and more as the source brightens.

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Title:
BeppoSAX discovery of the X-ray afterglow of GRB 971227
Authors:
Antonelli, L. A.; Fiore, F.; Amati, L.; Feroci, M.; Costa, E.; Frontera, F.; Gandolfi, G.; Giommi, P.; Piro, L.
Affiliation:
AA(Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monte Porzio Catone (RM), Italy; and BeppoSAX Science Data Center, Via Corcolle 19, I-00131 Roma, Italy), AB(Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monte Porzio (RM), Italy; and BeppoSAX Science Data Center, Via Corcolle 19, I-00131 Roma, Italy), AC(Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, I-40129 Bologna, Italy), AD(Istituto di Astrofisica Spaziale, CNR, Via Fosso del Cavaliere, I-00133 Roma, Italy), AE(Istituto di Astrofisica Spaziale, CNR, Via Fosso del Cavaliere, I-00133 Roma, Italy), AF(Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, I-40129 Bologna, Italy; and Dipartimento di Fisica, Università di Ferrara, Via Paradiso 11, I-44100 Ferrara, Italy), AG(BeppoSAX Scientific Operation Center, Telespazio, Via Corcolle 19, I-00131 Roma, Italy), AH(BeppoSAX Science Data Center, Via Corcolle 19, I-00131 Roma, Italy), AI(Istituto di Astrofisica Spaziale, CNR, Via Fosso del Cavaliere, I-00133 Roma, Italy)
Journal:
Astronomy and Astrophysics Supplement, v.138, p.435-436 (A&AS Homepage)
Publication Date:
09/1999
Origin:
A&AS
A&A Keywords:
GAMMA-RAYS: BURSTS, X-RAYS: OBSERVATION
Abstract Copyright:
(c) 1999: The European Southern Observatory (ESO)
Bibliographic Code:
1999A&AS..138..435A

Abstract

The BeppoSAX Narrow Field Instruments observed the region of sky containing GRB 971227 14 hours after the initial burst. A faint source (1SAXJ1257.3+5924) is detected in a position consistent with the BeppoSAX Wide Field Camera position, and disappears during the second half of the observation. In contrast to some other GRBs observed by BeppoSAX no optical and radio afterglows were unambiguously observed.

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Title:
BeppoSAX detection and follow-up of GRB 980425
Authors:
Pian, E.; Amati, L.; Antonelli, L. A.; Butler, R. C.; Costa, E.; Cusumano, G.; Danziger, J.; Feroci, M.; Fiore, F.; Frontera, F.; Giommi, P.; Masetti, N.; Muller, J. M.; Oosterbroek, T.; Owens, A.; Palazzi, E.; Piro, L.; Castro-Tirado, A.; Coletta, A.; dal Fiume, D.; del Sordo, S.; Heise, J.; Nicastro, L.; Orlandini, M.; Parmar, A.; Soffitta, P.; Torroni, V.; in 't Zand, J. J. M.
Affiliation:
AA( Istituto Te.S.R.E., CNR, via Gobetti 101, I-40129 Bologna, Italy), AB( Istituto Te.S.R.E., CNR, via Gobetti 101, I-40129 Bologna, Italy), AC(Osservatorio Astronomico di Roma, sede di Monteporzio Catone, Via Frascati 33, 00040 Monteporzio Catone, Italy), AD(Agenzia Spaziale Italiana, Viale Regina Margherita 120, Roma, Italy), AE(I.A.S., C.N.R., Via Fosso del Cavaliere, Area della Ricerca di Tor Vergata, I-00131 Rome, Italy), AF(I.F.C.A.I., CNR, via Ugo La Malfa 153, I-90146 Palermo, Italy), AG(Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, I-34131 Trieste, Italy), AH(I.A.S., C.N.R., Via Fosso del Cavaliere, Area della Ricerca di Tor Vergata, I-00131 Rome, Italy), AI(BeppoSAX Scientific Data Center, Via Corcolle 19, I-00131 Rome, Italy), AJ(Istituto Te.S.R.E., CNR, via Gobetti 101, I-40129 Bologna, Italy; and Dip. di Fisica, Univ. di Ferrara, Via Paradiso 11, I-44100 Ferrara, Italy), AK(BeppoSAX Scientific Data Center, Via Corcolle 19, I-00131 Rome, Italy), AL( Istituto Te.S.R.E., CNR, via Gobetti 101, I-40129 Bologna, Italy), AM(BeppoSAX Scientific Data Center, Via Corcolle 19, I-00131 Rome, Italy), AN(Astrophysics Division, SSD of ESA, ESTEC, P.O. Box 299, 2200 AG Noordwijk, The Netherlands), AO(Astrophysics Division, SSD of ESA, ESTEC, P.O. Box 299, 2200 AG Noordwijk, The Netherlands), AP( Istituto Te.S.R.E., CNR, via Gobetti 101, I-40129 Bologna, Italy), AQ(I.A.S., C.N.R., Via Fosso del Cavaliere, Area della Ricerca di Tor Vergata, I-00131 Rome, Italy), AR(IAA-CSIC, Granada, Spain and LAEFF-INTA, Madrid, Spain), AS(BeppoSAX Scientific Data Center, Via Corcolle 19, I-00131 Rome, Italy), AT( Istituto Te.S.R.E., CNR, via Gobetti 101, I-40129 Bologna, Italy), AU(I.F.C.A.I., CNR, via Ugo La Malfa 153, I-90146 Palermo, Italy), AV(Space Research Organization Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands), AW(I.F.C.A.I., CNR, via Ugo La Malfa 153, I-90146 Palermo, Italy), AX( Istituto Te.S.R.E., CNR, via Gobetti 101, I-40129 Bologna, Italy), AY(Astrophysics Division, SSD of ESA, ESTEC, P.O. Box 299, 2200 AG Noordwijk, The Netherlands), AZ(I.A.S., C.N.R., Via Fosso del Cavaliere, Area della Ricerca di Tor Vergata, I-00131 Rome, Italy), BA(BeppoSAX Scientific Data Center, Via Corcolle 19, I-00131 Rome, Italy), BB(Space Research Organization Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands)
Journal:
Astronomy and Astrophysics Supplement, v.138, p.463-464 (A&AS Homepage)
Publication Date:
09/1999
Origin:
A&AS
A&A Keywords:
GAMMA-RAYS: BURSTS
Abstract Copyright:
(c) 1999: The European Southern Observatory (ESO)
Bibliographic Code:
1999A&AS..138..463P

Abstract

We present BeppoSAX GRBM and WFC light curves of GRB 980425 and NFI follow-up data taken in 1998 April, May, and November. The first NFI observation has detected within the 8(') radius error box of the GRB an X-ray source positionally consistent with the supernova SN 1998bw, exploded within a day of GRB 980425, and a fainter X-ray source, not consistent with the position of the supernova. The former source is detected in the following NFI pointings and exhibits a decline of a factor of two in six months. If it is associated with SN 1998bw, this is the first detection of hard X-ray emission from a Type I supernova. The latter source exhibits only marginally significant variability. Based on these data, it is not possible to select either source as a firm candidate for the GRB counterpart.

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Title:
Spectral Evolution of PKS 2155-304 Observed with BeppoSAX during an Active Gamma-Ray Phase
Authors:
Chiappetti, L.; Maraschi, L.; Tavecchio, F.; Celotti, A.; Fossati, G.; Ghisellini, G.; Giommi, P.; Pian, E.; Tagliaferri, G.; Treves, A.; Urry, C. M.; Zhang, Y. H.
Journal:
The Astrophysical Journal, Volume 521, Issue 2, pp. 552-560. (ApJ Homepage)
Publication Date:
08/1999
Origin:
APJ
ApJ Keywords:
BL LACERTAE OBJECTS: INDIVIDUAL (PKS 2155-304), GAMMA RAYS: OBSERVATIONS, X-RAYS: GALAXIES
Abstract Copyright:
(c) 1999: The American Astronomical Society
Bibliographic Code:
1999ApJ...521..552C

Abstract

We present the results of BeppoSAX observations of PKS 2155-304 during an intense gamma-ray flare. The source was in a high X-ray state. A temporal analysis of the data reveals a tendency of the amplitude of variations to increase with energy and the presence of a soft lag with a timescale of the order 10^3 s. A curved continuum spectrum, with no evidence of spectral features, extends up to ~50 keV, while there is indication of a flatter component emerging at higher energies, consistent with the interpretation of the broadband spectral energy distribution (SED) due to synchrotron self-Compton emission from a single region. Notably, the fitting of the SED with such a model is consistent with an interpretation of the detected soft lag due to radiative cooling, supporting the idea that radiation losses play an important role in variability. The observed shifts of the SED peaks between the lowest and highest flux levels can be accounted for by an increase of the ``break'' energy in the relativistic particle spectrum. The model predicts emission at TeV energies in good agreement with the recently reported detection.

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Title:
The contribution of faint active galactic nuclei to the hard X-ray background
Authors:
Fiore, F.; La Franca, F.; Giommi, P.; Elvis, M.; Matt, G.; Comastri, A.; Molendi, S.; Gioia, I.
Affiliation:
AA(BeppoSAX Science Data Center, Via Corcolle 19, I-00131 Roma, Italy ), AB(Dipartimento di Fisica, Università degli Studi `Roma Tre', Via della Vasca Navale 84, I-00146 Roma, Italy ), AC(BeppoSAX Science Data Center, Via Corcolle 19, I-00131 Roma, Italy ), AD(Harvard-Smithsonian Center of Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA ), AE(Dipartimento di Fisica, Università degli Studi `Roma Tre', Via della Vasca Navale 84, I-00146 Roma, Italy ), AF(Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna, Italy ), AG(IFCTR/CNR, via Bassini 15, I-20133 Milano, Italy ), AH(IRA/CNR, via Gobetti 101, I-40129 Bologna, Italy )
Journal:
Monthly Notices of the Royal Astronomical Society, Volume 306, Issue 4, pp. L55-L60. (MNRAS Homepage)
Publication Date:
07/1999
Origin:
MNRAS
Abstract Copyright:
(c) 1999 The Royal Astronomical Society
Bibliographic Code:
1999MNRAS.306L..55F

Abstract

Hard X-ray selection is the most efficient way to discriminate between accretion-powered sources, such as active galactic nuclei (AGN), and sources dominated by starlight. Hard X-rays are also less affected than other bands by obscuration. We have therefore carried out the BeppoSAX High Energy Large Area Survey (HELLAS) in the largely unexplored 5-10 keV band, finding 180 sources in ~50 deg^2 of sky with flux>~5x10^-14 erg cm^-2 s^-1. After correction for the non-uniform sky coverage this corresponds to resolving about 30 per cent of the hard cosmic X-ray background (XRB). Here we report on a first optical spectroscopic identification campaign, finding 12 AGN out of 14 X-ray error boxes studied. Seven AGN show evidence for obscuration in X-ray and optical bands, a fraction higher than in previous ROSAT or ASCA-ROSAT surveys (at 95-99 and 90 per cent confidence levels respectively), thus supporting the scenario in which a significant fraction of the XRB is created by obscured AGN.

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Title:
1ES 1426+428
Authors:
Ghisellini, G.; Tagliaferri, G.; Giommi, P.
Journal:
IAU Circ., 7116, 3 (1999). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
03/1999
Origin:
CBAT
Objects:
1ES 1426+428
Bibliographic Code:
1999IAUC.7116....3G

Abstract

IAUC 7116 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
What can BeppoSAX tell us about X-ray spectra of BL Lacs?
Authors:
Wolter, Anna; Comastri, Andrea; Ghisellini, Gabriele; Giommi, Paolo; Guainazzi, Matteo; Maccacaro, Tommaso; Maraschi, Laura; Padovani, Paolo; Raiteri, Claudia; Tagliaferri, Gianpiero; Urry, C. Megan; Villata, Massimo
Affiliation:
AA(Osservatorio Astronomico di Brera, Milano, Italy), AB(Osservatorio Astronomico di Bologna, Bologna, Italy), AC(Osservatorio Astronomico di Brera, Milano, Italy), AD(A.S.I. BeppoSax Science Data Center, Roma, Italy), AE(A.S.I. BeppoSax Science Data Center, Roma, Italy), AF(Osservatorio Astronomico di Brera, Milano, Italy), AG(Osservatorio Astronomico di Brera, Milano, Italy), AH(Space Telescope Institute, Baltimore, USA), AI(Osservatorio Astronomico di Torino, Pino Torinese, Italy), AJ(Osservatorio Astronomico di Brera, Milano, Italy), AK(Space Telescope Institute, Baltimore, USA), AL(Osservatorio Astronomico di Torino, Pino Torinese, Italy)
Journal:
Nuclear Physics B Proceedings Supplements, Volume 69, Issue 1-3, p. 411-414.
Publication Date:
01/1999
Origin:
ELSEVIER
Abstract Copyright:
(c) 1999 Elsevier Science B.V. All rights reserved.
Bibliographic Code:
1999NuPhS..69..411W

Abstract

The wide energy band of BeppoSAX, together with its good energy resolution, offers the opportunity to investigate the overall X-ray spectra of BL Lacs, in order to measure in detail their shape, to establish where the Compton component becomes dominant over the synchrotron component. We present here preliminary results from the first year of BeppoSAX observations for a sample of soft X-ray selected BL Lacs. Ten XBL have been observed and analyzed so far: variability with respect to previous observations is very common, spectra are generally well fitted by a single power law, although a few examples of more complex spectra are present. We show BeppoSAX spectra and compare the results on the correlation between the X-ray slope and the peak frequency of the overall spectral energy distribution with those for a sample of radio selected BL Lacs.

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Title:
The BeppoSAX deep surveys
Authors:
Giommi, P.; Fiore, F.; Ricci, D.; Molendi, S.; Maccarone, M. C.; Comastri, A.
Affiliation:
AA(BeppoSAX Science Data Center, Rome, Italy), AB(BeppoSAX Science Data Center, Rome, Italy), AC(BeppoSAX Science Data Center, Rome, Italy), AD(IFCTR, CNR, Milano, Italy), AE(IFCAI, CNR, Palermo, Italy), AF()
Journal:
Nuclear Physics B Proceedings Supplements, Volume 69, Issue 1-3, p. 591-599.
Publication Date:
01/1999
Origin:
ELSEVIER
Abstract Copyright:
(c) 1999 Elsevier Science B.V. All rights reserved.
Bibliographic Code:
1999NuPhS..69..591G

Abstract

We present the preliminary results of a survey that makes use of several deep exposures obtained with the X-ray telescopes of the BeppoSAX satellite. The survey limiting sensitivity is 5x10-14ergcm-2s-1 in the 2-10keV band and 7x10-14ergcm-2s-1 in the harder 5-10keV band. We find that the 2-10keV LogN-LogS is consistent with that determined in ASCA surveys. The counts in the 5-10keV band imply either a very hard average spectral slope or the existence of a population of heavily absorbed sources that can hardly be detected in soft X-ray surveys. A sample of 83 serendipitous sources has been compiled from a systematic search in 50 MECS images. The analysis of the hardness ratio of this sample also implies very hard or heavily cutoff spectral shapes.

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Title:
The BeppoSAX source catalog
Authors:
Ricci, D.; Fiore, F.; Giommi, P.
Affiliation:
AA(Beppo-SAX Science Data Center, Via Corcolle 19, 00131 Roma, Italy), AB(Beppo-SAX Science Data Center, Via Corcolle 19, 00131 Roma, Italy), AC(Beppo-SAX Science Data Center, Via Corcolle 19, 00131 Roma, Italy)
Journal:
Nuclear Physics B Proceedings Supplements, Volume 69, Issue 1-3, p. 618-621.
Publication Date:
01/1999
Origin:
ELSEVIER
Abstract Copyright:
(c) 1999 Elsevier Science B.V. All rights reserved.
Bibliographic Code:
1999NuPhS..69..618R

Abstract

We present source search strategies and methodologies to build a catalog of sources detected in the BeppoSAX imaging instruments. We present a preliminary database constructed using SVP and AO1 proprietary data. We show the results of the correlation of this database with a large number of other astronomical databases (e.g. NVSS, VERON, WGACAT, RASS, etc).

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Title:
BeppoSAX observations of 1 Jy BL Lacertae objects
Authors:
Padovani, Paolo; Giommi, Paolo; Comastri, Andrea; Ghisellini, Gabriele; Maccacaro, Tommaso; Mantovani, Franco; Maraschi, Laura; Stanghellini, Carlo; Tagliaferri, Gianpiero; Urry, C. Megan; Wolter, Anna
Affiliation:
AA(Space Telescope Science Institute, Baltimore, USA), AB(SAX/SDC, ASI, Roma, Italy), AC(Osservatorio Astronomico di Bologna, Bologna, Italy), AD(Osservatorio Astronomico di Brera/Merate, Merate, Italy), AE(Osservatorio Astronomico di Brera/Merate, Merate, Italy), AF(Istituto di Radioastronomia, Bologna, Italy), AG(Osservatorio Astronomico di Brera/Merate, Merate, Italy), AH(Istituto di Radioastronomia, Bologna, Italy), AI(Osservatorio Astronomico di Brera/Merate, Merate, Italy), AJ(Space Telescope Science Institute, Baltimore, USA), AK(Osservatorio Astronomico di Brera/Merate, Merate, Italy)
Journal:
Nuclear Physics B Proceedings Supplements, Volume 69, Issue 1-3, p. 431-434.
Publication Date:
01/1999
Origin:
ELSEVIER
Abstract Copyright:
(c) 1999 Elsevier Science B.V. All rights reserved.
Bibliographic Code:
1999NuPhS..69..431P

Abstract

Preliminary results on BeppoSAX LECS and MECS observations of BL Lacertae objects selected from the 1 Jy sample are presented. All sources of the LBL type, that is, characterized by a peak in their multifrequency spectra at infrared/optical energies, seem to show a relatively flat (αX~0.7-0.8) X-ray spectrum. This is in agreement with the supposed dominance of inverse Compton emission in the X-ray band of these sources.

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Title:
X-ray luminosity and spectral variability in the TEV BL Lac 1ES2344+514
Authors:
Giommi, P.; Padovani, P.; Perlman, E.
Affiliation:
AA(BeppoSAX Science Data Center, Rome, Italy), AB(Space Telescope Science Institute, Baltimore, USA), AC(Space Telescope Science Institute, Baltimore, USA)
Journal:
Nuclear Physics B Proceedings Supplements, Volume 69, Issue 1-3, p. 407-410.
Publication Date:
01/1999
Origin:
ELSEVIER
Abstract Copyright:
(c) 1999 Elsevier Science B.V. All rights reserved.
Bibliographic Code:
1999NuPhS..69..407G

Abstract

The results of a series of five BeppoSAX observations of the TeV BL Lac object 1ES2344+514 are briefly presented. Large amplitude luminosity variability, associated to impressive spectral changes in the hard X-rays, have been found. The shape of the lightcurve depends on energy, with the flare starting and ending in the hard band, but with maximum intensity possibly reached earlier in the soft X-rays. The luminosity and spectral changes may be due to a shift of the peak of the synchrotron emission from the soft X-rays to the hard X-ray band similar to that detected during BeppoSAX observations of MKN 501.

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Title:
A BeppoSAX wide field camera secondary observations results database
Authors:
Muller, J. M.; Giommi, P.
Affiliation:
AA(SRON, Sorbonnelaan 2, 3584 CA Utrecht, Netherlands), AB(Beppo-SAX Science Data Centre, Via Corcolle 19, 00131 Roma, Italy)
Journal:
Nuclear Physics B Proceedings Supplements, Volume 69, Issue 1-3, p. 622-624.
Publication Date:
01/1999
Origin:
ELSEVIER
Abstract Copyright:
(c) 1999 Elsevier Science B.V. All rights reserved.
Bibliographic Code:
1999NuPhS..69..622M

Abstract

We demonstrate the potential of the database at SAX-SDC which will contain the analysis results of all BSAX Wide Field Camera secondary observations.

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Title:
Beppo SAX observations of PKS 2155-304 during an active gamma-ray state.
Authors:
Maraschi, L.; Chiappetti, L.; Tavecchio, F.; Celotti, A.; Fossati, G.; Ghisellini, G.; Giommi, P.; Pian, E.; Tagliaferri, G.; Treves, A.; Zhang, Y. H.
Journal:
Mem. Soc. Astron. Ital., 70, 193-196 (1999)
Publication Date:
00/1999
Origin:
SIMBAD
Bibliographic Code:
1999MmSAI..70..193M

Abstract

Not Available

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Title:
The BeppoSAX GRATIS survey.
Authors:
Perri, M.; Giommi, P.; Fiore, F.; Antonelli, L. A.
Journal:
Mem. Soc. Astron. Ital., 70, 267-268 (1999)
Publication Date:
00/1999
Origin:
SIMBAD
Bibliographic Code:
1999MmSAI..70..267P

Abstract

Not Available

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Title:
BeppoSAX NFI observation of GRB990705.
Authors:
Amati, L.; Frontera, F.; Antonelli, L. A.; Cusumano, G.; Gandolfi, G.; Costa, E.; Daniele, M. R.; Giommi, P.
Journal:
GRB Circular Network, 384, 1 (1999)
Publication Date:
00/1999
Origin:
SIMBAD
Bibliographic Code:
1999GCN...384....1A

Abstract

Not Available

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Title:
X-Ray Surveys
Authors:
Giommi, P.; Fiore, F.; Perri, M.
Journal:
Astrophysical Letters and Communications, Vol. 39, p.173
Publication Date:
00/1999
Origin:
ADS
Bibliographic Code:
1999ApL&C..39..173G

Abstract

Not Available

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Title:
The BeppoSAX Mission Planning Component
Authors:
Ricci, D.; Rebecchi, S.; Capalbi, M.; Coletta, A.; Giommi, P.; Ricci, R.; Spoliti, G.
Journal:
Astrophysical Letters and Communications, Vol. 39, p.445
Publication Date:
00/1999
Origin:
ADS
Bibliographic Code:
1999ApL&C..39..445R

Abstract

Not Available

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Title:
The Deep X-Ray Radio Blazar Survey (DXRBS)
Authors:
Padovani, Paolo; Perlman, Eric; Giommi, Paolo; Sambruna, Rita; Jones, Laurence R.; Tzioumis, Anastasios; Reynolds, John
Affiliation:
AA(Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA, and Affiliated to the Astrophysics Division, Space Science Department, European Space Agency, and Dipartimento di Fisica, II Universitàa di Roma ``Tor Vergata'', Italy), AB(Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA), AC(SAX Science Data Center, ASI, Viale Regina Margherita 202, I-00198, Italy), AD(Pennsylvania State University, Department of Astronomy, 525 Davey Lab, University Park, PA 16803), AE(School of Physics & Astronomy, Univ. of Birmingham, Birmingham B15 2TT, UK), AF(Australia Telescope National Facility, CSIRO, PO Box 76, Epping NSW 2121, Australia), AG(Australia Telescope National Facility, CSIRO, PO Box 76, Epping NSW 2121, Australia)
Journal:
Looking Deep in the Southern Sky, Proceedings of the ESO/Australia Workshop held at Sydney, Australia, 10-12 December 1997. Edited by Faffaella Morganti and Warrick J. Couch. Berlin: Springer-Verlag, 1999. p. 187.
Publication Date:
00/1999
Origin:
AUTHOR
Bibliographic Code:
1999ldss.work..187P

Abstract

We have undertaken a survey for blazars by correlating the ROSAT WGACAT database with publicly available radio catalogs, restricting our candidate list to serendipitous flat-spectrum sources (αr <= 0.7, fν ~ ν-α). We discuss here our survey methods, identification procedure and first results. Our survey is found to be ~95% efficient at finding blazars, a figure which is comparable to or greater than that achieved by other radio and X-ray survey techniques. DXRBS provides a much more uniform coverage of the parameter space occupied by blazars than any previous survey. Particularly important is the identification of a large population of flat-spectrum radio quasars with ratios of X-ray to radio luminosity >~ 10-6 (αrx <~ 0.78) and of many low-luminosity flat-spectrum radio quasars. Moreover, DXRBS fills in the region of parameter space between X-ray selected and radio-selected samples of BL Lacs.

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Title:
The BeppoSAX "hellas" Survey
Authors:
Fiore, F.; Giommi, P.; La Franca, F.; Matt, G.; Perola, C. G.; Comastri, A.; Molendi, S.; Elvis, M.; Gioa, I.; Tamburelli, F.; Ricci, D.; Pompilio, F.
Journal:
Astrophysical Letters and Communications, Vol. 39, p.189
Publication Date:
00/1999
Origin:
ADS
Bibliographic Code:
1999ApL&C..39..189F

Abstract

Not Available

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Title:
X-Ray Spectral Evolution of MKN421 in a Very High State
Authors:
Malizia, A.; Fiore, F.; Giommi, P.; Capalbi, M.; Tesseri, A.; Gandolfi, G.; Rebecchi, S.; Ricci, D.; di Ciolo, L.; Smith, S. M. J.; Celidonio, G.; Antonelli, A. L.; Ricci, R.; Torroni, V.; Spoliti, G.; Muller, M. J.; Butler, R. C.; Piro, L.
Journal:
Astrophysical Letters and Communications, Vol. 39, p.69
Publication Date:
00/1999
Origin:
ADS
Bibliographic Code:
1999ApL&C..39...69M

Abstract

Not Available

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Title:
Bright Radio Galaxies with BeppoSAX
Authors:
Grandi, P.; Maraschi, L.; Guainazzi, M.; Haardt, F.; Matt, G.; Massaro, E.; Urry, M. C.; Bassani, L.; Giommi, P.
Journal:
Astrophysical Letters and Communications, Vol. 39, p.45
Publication Date:
00/1999
Origin:
ADS
Bibliographic Code:
1999ApL&C..39...45G

Abstract

Not Available

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Title:
The Sedentary Multi-Frequency Survey: Preliminary Results on the Statistical Identification and Cosmological Properties of a Large Sample of HBL BL Lacs
Authors:
Giommi, P.; et al.
Journal:
BL Lac Phenomenon, a conference held 22-26 June, 1998 in Turku, Finland, p. 517.
Publication Date:
00/1999
Origin:
AUTHOR
Bibliographic Code:
1999bllp.conf..517G

Abstract

Not Available

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Title:
New Constraints on the Spectral Energy Distribution of Blazars from the Deep X-ray Radio Blazar Survey (DXRBS)
Authors:
Padovani, P.; Perlman, E. S.; Giommi, P.; Sambruna, R. M.
Affiliation:
AA(ESA, STScI), AB(STScI), AC(BeppoSAX SDC), AD(Penn. State University)
Journal:
American Astronomical Society, 193rd AAS Meeting, #107.16; Bulletin of the American Astronomical Society, Vol. 30, p.1413
Publication Date:
12/1998
Origin:
AAS
Abstract Copyright:
(c) 1998: American Astronomical Society
Bibliographic Code:
1998AAS...19310716P

Abstract

The Deep X-ray Radio Blazar Survey (DXRBS) will provide, when complete, a sample of about 300 blazars. The candidate list is obtained by correlating the ROSAT WGACAT database with several radio catalogs and restricting the selection to flat spectrum radio sources (alpha_r <= 0.70). The selection criteria result in a very high efficiency ( ~ 95%) at finding flat-spectrum radio quasars and BL Lacertae objects. Identification of the sources is ~ 80% complete. One of the most interesting discoveries so far is the identification of a large population of flat-spectrum radio quasars ( ~ 25% of all DXRBS quasars) with ratios of X-ray to radio luminosity ga 10(-6) (alpha_rx la 0.78; Perlman et al. 1998). These ``X-ray strong'' quasars, which previous surveys could not have detected, might be the high-luminosity version of the high-energy peaked BL Lacs, which have synchrotron peak emission in the UV/X-ray band. Here we present a detailed investigation of the spectral energy distribution of this newly discovered class of blazars. We also compare our results with the predictions of recent models aimed at unifying blazars in terms of the position of the synchrotron peak and of power.

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Title:
GRB 981226
Authors:
Frontera, F.; Montanari, E.; Antonelli, L. A.; Giommi, P.; Piro, L.; Daniele, M. R.; Coletta, A.; de Libero, C.
Journal:
IAU Circ., 7078, 2 (1998). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
12/1998
Origin:
CBAT
Objects:
GRB 981226
Bibliographic Code:
1998IAUC.7078....2F

Abstract

IAUC 7078 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
PKS 2005-489
Authors:
Tagliaferri, G.; Ghisellini, G.; Maraschi, L.; Giommi, P.
Journal:
IAU Circ., 7055, 2 (1998). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
11/1998
Origin:
CBAT
Objects:
PKS 2005-489
Bibliographic Code:
1998IAUC.7055....2T

Abstract

IAUC 7055 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
The discovery of 13 s X-ray pulsations from the hydrogen depleted subdwarf O6 star binary HD49798
Authors:
Israel, G. L.; Stella, L.; Angelini, L.; White, N. E.; Kallman, T. R.; Giommi, P.; Treves, A.
Affiliation:
AA(International School for Advanced Studies (SISSA-ISAS), Via Beirut 2-4 I-34014 Trieste, israel@vega.sissa.it treves@astmiu.mi.astro.itItaly), AB(Osservatorio Astronomico di Roma, V. dell'Osservatorio 2 I-00040 Monteporzio Catone (Roma), stella@coma.mporzio.astro.itItaly), AC(Laboratory for High Energy Astrophysics, Code 662, NASA Goddard Space Flight Center Greenbelt, MD 20771, white@adhoc.gsfc.nasa.gov, angelini@lheavx.gsfc.nasa.gov, tim@xstar.gsfc.nasa.govUSA), AD(Laboratory for High Energy Astrophysics, Code 662, NASA Goddard Space Flight Center Greenbelt, MD 20771, white@adhoc.gsfc.nasa.gov, angelini@lheavx.gsfc.nasa.gov, tim@xstar.gsfc.nasa.govUSA), AE(Laboratory for High Energy Astrophysics, Code 662, NASA Goddard Space Flight Center Greenbelt, MD 20771, white@adhoc.gsfc.nasa.gov, angelini@lheavx.gsfc.nasa.gov, tim@xstar.gsfc.nasa.govUSA), AF(SAX Science Data Center, ASI, Viale Regina Margherita 202 I-00198 Roma, giommi@sax.sdc.asi.itItaly), AG(International School for Advanced Studies (SISSA-ISAS), Via Beirut 2-4 I-34014 Trieste, israel@vega.sissa.it treves@astmiu.mi.astro.itItaly)
Journal:
Advances in Space Research, Volume 22, Issue 7, p. 1035-1038. (AdSpR Homepage)
Publication Date:
10/1998
Origin:
ELSEVIER
Abstract Copyright:
(c) Elsevier Science B.V. All rights reserved.
Bibliographic Code:
1998AdSpR..22.1035I

Abstract

Not Available

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Title:
The discovery of 12-min X-ray pulsations from 1WGA J1958.2+3232
Authors:
Israel, G. L.; Angelini, L.; Campana, S.; Giommi, P.; Stella, L.; White, N. E.
Affiliation:
AA(Osservatorio Astronomico di Roma, Vicolo dell'Osservatorio 2, I-00040 Monteporzio Catone, Roma, Italy), AB(Laboratory for High Energy Astrophysics, Code 662, NASA - Goddard Space Flight Center, Greenbelt, MD 20771, USA), AC(Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate, Lecco, Italy), AD(SAX Science Data Center, ASI, Viale Regina Margherita 202, I-00198 Roma, Italy), AE(Osservatorio Astronomico di Roma, Vicolo dell'Osservatorio 2, I-00040 Monteporzio Catone, Roma, Italy), AF(Laboratory for High Energy Astrophysics, Code 662, NASA - Goddard Space Flight Center, Greenbelt, MD 20771, USA)
Journal:
Monthly Notices of the Royal Astronomical Society, Volume 298, Issue 2, pp. 502-506. (MNRAS Homepage)
Publication Date:
08/1998
Origin:
MNRAS
MNRAS Keywords:
STARS: INDIVIDUAL: 1WGA J1958.2+3232, NOVAE, CATACLYSMIC VARIABLES, PULSARS: GENERAL, STARS: ROTATION, X-RAYS: STARS
Abstract Copyright:
(c) 1998 The Royal Astronomical Society
Bibliographic Code:
1998MNRAS.298..502I

Abstract

During a systematic search for periodic signals in a sample of ROSAT PSPC (0.1-2.4keV) light curves, we have discovered ~12-min large-amplitude X-ray pulsations in 1WGA J1958.2+3232, an X-ray source which lies close to the Galactic plane. The energy spectrum is well fitted by a power law with a photon index of 0.8, corresponding to an X-ray flux level of ~10^-12 erg cm^-2 s^-1. The source is probably a long-period, low-luminosity X-ray pulsar, similar to X Per, or an intermediate polar.

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Title:
BeppoSAX spectral survey of soft X-ray selected BL Lacertae objects
Authors:
Wolter, A.; Comastri, A.; Ghisellini, G.; Giommi, P.; Guainazzi, M.; Maccacaro, T.; Maraschi, L.; Padovani, P.; Raiteri, C. M.; Tagliaferri, G.; Urry, C. M.; Villata, M.
Affiliation:
AA(Osservatorio Astronomico di Brera Via Brera, 28 I-20121 Milano, Italy), AB(Osservatorio Astronomico di Bologna, Via Zamboni 33, I-40126 Bologna, Italy), AC(Osservatorio Astronomico di Brera Via Brera, 28 I-20121 Milano, Italy), AD(A.S.I., Beppo-SAX Science Data Center, Via Corcolle 19, I-00131 Roma, Italy), AE(A.S.I., Beppo-SAX Science Data Center, Via Corcolle 19, I-00131 Roma, Italy), AF(Osservatorio Astronomico di Brera Via Brera, 28 I-20121 Milano, Italy), AG(Osservatorio Astronomico di Brera Via Brera, 28 I-20121 Milano, Italy), AH(Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD. 21218, USA), AI(Osservatorio Astronomico di Torino, Strada Osservatorio 20, I-10025 Pino Torinese (TO), Italy), AJ(Osservatorio Astronomico di Brera Via Brera, 28 I-20121 Milano, Italy), AK(Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD. 21218, USA), AL(Osservatorio Astronomico di Torino, Strada Osservatorio 20, I-10025 Pino Torinese (TO), Italy)
Journal:
Astronomy and Astrophysics, v.335, p.899-911 (1998) (A&A Homepage)
Publication Date:
07/1998
Origin:
A&A
A&A Keywords:
BL LACERTAE OBJECTS: GENERAL, X-RAYS: GALAXIES
Abstract Copyright:
(c) 1998: Astronomy & Astrophysics
Bibliographic Code:
1998A&A...335..899W

Abstract

We present X-ray spectra obtained with BeppoSAX (Satellite per Astronomia X) of 10 BL Lac objects, selected from the Einstein Medium Sensitivity and Slew Surveys. We find that in about half of the objects a fit in the 0.1-10 keV range with a single power law and free absorption yields values of N_H larger than the Galactic ones. In most of these cases, however, broken power law fits with N_H fixed at the Galactic values yield an alternative, better description of the data and indicate a steepening of the spectrum with increasing energy. One object (1ES1101-232) is detected up to ~ 100 keV. Its spectral energy distribution (SED) peaks in the medium energy X-ray band. For each object we compute the peak frequency of the SED from multifrequency data. The spectral indices alpha_x in the 2-10 keV band (F_nu ~ nu (-alpha_x ) ) are smaller (i.e. flatter spectrum) for objects with higher peak frequencies. We therefore confirm and extend to higher energies the behavior already known for X-ray selected BL Lac objects in the ROSAT band. We do not find spectral indices smaller than 1; however, the flat distribution of alpha_x and the correlation between alpha_x and peak frequency found from our data suggest that a number of objects may exist, which in the quiescent status have flatter spectrum and peak frequency in the hard X-ray range.

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Title:
W Comae Berenices
Authors:
Tagliaferri, G.; Ghisellini, G.; Giommi, P.
Journal:
IAU Circ., 6925, 3 (1998). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
06/1998
Origin:
CBAT
Objects:
W Com
Bibliographic Code:
1998IAUC.6925....3T

Abstract

IAUC 6925 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
The complex 0.1-100 keV X-ray spectrum of PKS 2155-304
Authors:
Giommi, P.; Fiore, F.; Guainazzi, M.; Feroci, M.; Frontera, F.; Ghisellini, G.; Grandi, P.; Maraschi, L.; Mineo, T.; Molendi, S.; Orr, A.; Piraino, S.; Segreto, A.; Tagliaferri, G.; Treves, A.
Affiliation:
AA({BeppoSAX Science Data Center, ASI, Via Corcolle 19, I-00131 Roma, Italy }), AB({BeppoSAX Science Data Center, ASI, Via Corcolle 19, I-00131 Roma, Italy }; {Osservatorio Astronomico di Roma, Monteporzio Catone, Italy }), AC({BeppoSAX Science Data Center, ASI, Via Corcolle 19, I-00131 Roma, Italy }), AD({Istituto di Astrofisica Spaziale, CNR, Via Enrico Fermi 21, I-00044 Frascati, Italy }), AE({Dipartimento di Fisica, Universitadi Ferrara, Via Paradiso 12, I-44100 Ferrara, Italy }; {Istituto TESRE, CNR, Via Gobetti 101, I-40129 Bologna, Italy }), AF({Osservatorio Astronomico di Brera, via Brera 28, I-20121 Milano, Italy }), AG({Istituto di Astrofisica Spaziale, CNR, Via Enrico Fermi 21, I-00044 Frascati, Italy }), AH({Osservatorio Astronomico di Brera, via Brera 28, I-20121 Milano, Italy }), AI({Istituto di Fisica Cosmica ed Applicazioni dell'Informatica, C.N.R. Via Ugo La Malfa 156, Palermo, Italy }), AJ({Istituto di Fisica Cosmica, CNR, Via Bassini 15, I-20133 Milano, Italy }; {BeppoSAX Science Data Center, ASI, Via Corcolle 19, I-00131 Roma, Italy }), AK({Space Science Department of ESA, ESTEC, Keplerlaan, Noordwijk, The Netherlands }), AL({Istituto di Fisica Cosmica ed Applicazioni dell'Informatica, C.N.R. Via Ugo La Malfa 156, Palermo, Italy }), AM({Istituto di Fisica Cosmica ed Applicazioni dell'Informatica, C.N.R. Via Ugo La Malfa 156, Palermo, Italy }), AN({Osservatorio Astronomico di Brera, via Brera 28, I-20121 Milano, Italy }), AO({Universita' di Milano, sede di Como, Via Lucini 3, I-22100 Como, Italy })
Journal:
Astronomy and Astrophysics, v.333, p.L5-L8 (1998) (A&A Homepage)
Publication Date:
05/1998
Origin:
A&A
A&A Keywords:
GALAXIES, ACTIVE
Abstract Copyright:
(c) 1998: Astronomy & Astrophysics
Bibliographic Code:
1998A&A...333L...5G

Abstract

A long (>100,000 seconds) observation of the bright BL Lac object PKS 2155-304 has been carried out with the Narrow Field Instruments of the BeppoSAX satellite as part of the Science Verification Phase. The source was detected between 0.1 and about 100keV at an intermediate intensity level compared to previous observations. The unique spectral coverage of BeppoSAX has allowed us to detect a number of spectral features. Between 0.1 and 10keV the spectrum can be well described by a convex spectrum with (energy) slope gradually steepening from 1.1 to 1.6. At higher energies evidence for a sharp spectral hardening is found, while in the soft X-rays (0.1-1.0keV) some evidence for an absorption feature was found. Indication for an emission line at 6.4keV in the source rest frame is present. Repeated variability of ~ 20-30% around the mean flux is clearly detected on time scales of a few hours. From the symmetry and timescale of the observed variations we derive limits on the magnetic field and on the maximum energy of the emitting particles, implying that PKS 2155-304 should not be bright at TeV energies.

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Title:
The Deep X-Ray Radio Blazar Survey. I. Methods and First Results
Authors:
Perlman, Eric S.; Padovani, Paolo; Giommi, Paolo; Sambruna, Rita; Jones, Laurence R.; Tzioumis, Anastasios; Reynolds, John
Affiliation:
AA(Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218; perlman@stsci.edu), AB(Dipartimento di Fisica, Il Università di Roma ``Tor Vergata,'' via della Ricerca Scientifica 1, I-00133 Roma, Italy), AC(SAX Science Data Center, Agenzia Spaziale Italiana, viale Regina Margherita 202, I-00198 Roma, Italy), AD(Laboratory for High Energy Astrophysics, Code 660.2, NASA Goddard Space Flight Center, Greenbelt, MD 20771), AE(School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, England, UK), AF(Australia Telescope National Facility, CSIRO, P.O. Box 76, Epping, NSW 2121, Australia), AG(Australia Telescope National Facility, CSIRO, P.O. Box 76, Epping, NSW 2121, Australia)
Journal:
The Astronomical Journal, Volume 115, Issue 4, pp. 1253-1294. (AJ Homepage)
Publication Date:
04/1998
Origin:
AJ
AJ Keywords:
GALAXIES: BL LACERTAE OBJECTS: GENERAL, GALAXIES: QUASARS: GENERAL, RADIO CONTINUUM, SURVEYS
Abstract Copyright:
The American Astronomical Society
Bibliographic Code:
1998AJ....115.1253P

Abstract

We have undertaken a survey, the Deep X-Ray Radio Blazar Survey (DXRBS), of archived, pointed ROSAT Position Sensitive Proportional Counter data for blazars by correlating the ROSAT WGACAT database with several publicly available radio catalogs, restricting our candidate list to serendipitous flat radio spectrum sources (alpha_r <= 0.70, where S_nu ~ nu^-alpha_r . We discuss our survey methods, identification procedure, and first results. Our survey is found to be ~95% efficient at finding flat-spectrum radio-loud quasars (FSRQs; 59 of our first 85 identifications) and BL Lacertae objects (22 of our first 85 identifications), a figure that is comparable to or greater than that achieved by other radio and X-ray survey techniques. The identifications presented here show that all previous samples of blazars (even when taken together) did not representatively survey the blazar population, missing critical regions of (L_X, L_R) parameter space within which large fractions of the blazar population lie. Particularly important is the identification of a large population of FSRQs (>~25% of DXRBS FSRQs) with ratios of X-ray to radio luminosity >~10^-6 (alpha_rx <~ 0.78). In addition, as a result of our greater sensitivity, the DXRBS has already more than doubled the number of FSRQs in complete samples with 5 GHz (radio) luminosities between 10^31.5 and 10^33.5 ergs s^-1 Hz^-1, and fills in the region of parameter space between X-ray-selected and radio-selected samples of BL Lac objects. The DXRBS is the very first sample to contain statistically significant numbers of blazars at low luminosities, approaching what should be the lower end of the FSRQ luminosity function. Based on observations collected at the European Southern Observatory, La Silla, Chile; Kitt Peak National Observatory; Cerro Tololo Inter-American Observatory; and the Australia Telescope National Facility.

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Title:
BeppoSAX follow-up search for the X-ray afterglow of GRB970111
Authors:
Feroci, M.; Antonelli, L. A.; Guainazzi, M.; Muller, J. M.; Costa, E.; Piro, L.; in 't Zand, J. J. M.; Frontera, F.; dal Fiume, D.; Nicastro, L.; Orlandini, M.; Palazzi, E.; Zavattini, G.; Giommi, P.; Parmar, A. N.; Owens, A.; Castro-Tirado, A. J.; Maccarone, M. C.; Butler, R. C.
Affiliation:
AA(Istituto di Astrofisica Spaziale, CNR, Via Fosso del Cavaliere, I-00133 Roma, Italy), AB(BeppoSAX Scientific Data Center, Via Corcolle 19, I-00131 Roma, Italy), AC(BeppoSAX Scientific Data Center, Via Corcolle 19, I-00131 Roma, Italy), AD(BeppoSAX Scientific Data Center, Via Corcolle 19, I-00131 Roma, Italy; and Space Research Organization in the Netherlands, Sorbonnelaan 2, 3584 CA, Utrecht, The Netherlands), AE(Istituto di Astrofisica Spaziale, CNR, Via Fosso del Cavaliere, I-00133 Roma, Italy), AF(Istituto di Astrofisica Spaziale, CNR, Via Fosso del Cavaliere, I-00133 Roma, Italy), AG(Space Research Organization in the Netherlands, Sorbonnelaan 2, 3584 CA, Utrecht, The Netherlands), AH(Space Research Organization in the Netherlands, Sorbonnelaan 2, 3584 CA, Utrecht, The Netherlands), AI(Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, I-40129 Bologna, Italy; and Dipartimento di Fisica, Universita di Ferrara, Via Paradiso 11, I-44100 Ferrara, Italy), AJ(Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, I-40129 Bologna, Italy), AK(Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, I-40129 Bologna, Italy), AL(Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, I-40129 Bologna, Italy), AM(Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, I-40129 Bologna, Italy), AN(Dipartimento di Fisica, Universita di Ferrara, Via Paradiso 11, I-44100 Ferrara, Italy), AO(BeppoSAX Scientific Data Center, Via Corcolle 19, I-00131 Roma, Italy), AP(Astrophysics Division, Space Science Department of ESA, ESTEC, P.O. Box 299, 2200 AG, Noordwijk, The Netherlands), AQ(Astrophysics Division, Space Science Department of ESA, ESTEC, P.O. Box 299, 2200 AG, Noordwijk, The Netherlands), AR(Laboratorio de Astrofisica Espacial y Fisica Fundamental, INTA, Madrid, Spain), AS(Istituto Fisica Cosmica e Applicazioni Informatica, CNR, Via U. LaMalfa 153, I-90146 Palermo, Italy), AS(Agenzia Spaziale Italiana, Viale Regina Margherita 202, I-00162 Roma, Italy)
Journal:
Astronomy and Astrophysics, v.332, p.L29-L33 (1998) (A&A Homepage)
Publication Date:
04/1998
Origin:
A&A
A&A Keywords:
GAMMA RAYS: BURSTS, X-RAYS: BURSTS
Bibliographic Code:
1998A&A...332L..29F

Abstract

The BeppoSAX satellite has recently opened a new way towards the solution of the long standing gamma-ray bursts' (GRBs) enigma, providing accurate coordinates few hours after the event thus allowing for multiwavelength follow-up observational campaigns. The BeppoSAX Narrow Field Instruments observed the region of sky containing GRB970111 16 hours after the burst. In contrast to other GRBs observed by BeppoSAX no bright afterglow was unambiguously observed. A faint source (1SAXJ1528.1+1937) is detected in a position consistent with the BeppoSAX Wide Field Camera position, but unconsistent with the IPN annulus. Whether 1SAXJ1528.1+1937 is associated with GRB970111 or not, the X-ray intensity of the afterglow is significantly lower than expected, based on the properties of the other BeppoSAX GRB afterglows. Given that GRB970111 is one of the brightest GRBs observed, this implies that there is no obvious relation between the GRB gamma-ray peak flux and the intensity of the X-ray afterglow.

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Title:
1SAX J0104.5+5828
Authors:
Ricci, R.; Smith, M.; Soffitta, P.; Piro, L.; Giommi, P.; Rebecchi, S.; Muller, J. M.; Gennaro, G.
Journal:
IAU Circ., 6816, 1 (1998). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
01/1998
Origin:
CBAT
Objects:
1SAX J0104.5+5828
Bibliographic Code:
1998IAUC.6816....1R

Abstract

IAUC 6816 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
BeppoSAX Observations of Unprecedented Synchrotron Activity in the BL Lacertae Object Markarian 501
Authors:
Pian, Elena; Vacanti, Giuseppe; Tagliaferri, Gianpiero; Ghisellini, Gabriele; Maraschi, Laura; Treves, Aldo; Urry, Megan; Fiore, Fabrizio; Giommi, Paolo; Palazzi, Eliana; Chiappetti, Lucio; Sambruna, Rita M.
Journal:
Astrophysical Journal Letters v.492, p.L17 (ApJ Homepage)
Publication Date:
01/1998
Origin:
APJ
ApJ Keywords:
GALAXIES: BL LACERTAE OBJECTS: INDIVIDUAL NAME: MARKARIAN 501, GALAXIES: ACTIVE, GALAXIES: NUCLEI, RADIATION MECHANISMS: NONTHERMAL, X-RAYS: GALAXIES
Abstract Copyright:
(c) 1998: The American Astronomical Society
Bibliographic Code:
1998ApJ...492L..17P

Abstract

The BL Lacertae object Markarian 501, one of only three extragalactic sources (with Mrk 421 and 1ES 2344+514) so far detected at TeV energies, was observed with the BeppoSAX satellite in 1997 April 7, 11, and 16 during a phase of high activity at TeV energies, as monitored with the Whipple, HEGRA, and CAT Cherenkov telescopes. Over the whole 0.1-200 keV range, the spectrum was exceptionally hard ( alpha <=1 , with F_{ nu }~ nu ^{- alpha } ), indicating that the X-ray power output peaked at (or above) ~100 keV. This represents a shift of at least 2 orders of magnitude with respect to previous observations of Mrk 501, a behavior never seen before in this or any other blazar. The overall X-ray spectrum hardens with increasing intensity, and at each epoch it is softer at larger energies. The correlated variability from soft X-rays to the TeV band points to models in which the same population of relativistic electrons produces the X-ray continuum via synchrotron radiation and the TeV emission by inverse Compton scattering of the synchrotron photons or other seed photons. For the first time in any blazar, the synchrotron power is observed to peak at hard X-ray energies. The large shift of the synchrotron peak frequency with respect to previous observations of Mrk 501 implies that intrinsic changes in the relativistic electron spectrum caused the increase in emitted power. Due to the very high electron energies, the inverse Compton process is limited by the Klein-Nishina regime. This implies a quasi-linear (as opposed to quadratic) relation of the variability amplitude in the TeV and hard X-ray ranges (for the synchrotron self-Compton model) and an increase of the inverse Compton peak frequency smaller than that of the synchrotron peak frequency.

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Title:
X-Ray Spectral Survey of WGACAT Quasars. II. Optical and Radio Properties of Quasars with Low-Energy X-Ray Cutoffs
Authors:
Elvis, Martin; Fiore, Fabrizio; Giommi, Paolo; Padovani, Paolo
Journal:
Astrophysical Journal v.492, p.91 (ApJ Homepage)
Publication Date:
01/1998
Origin:
APJ
ApJ Keywords:
GALAXIES: QUASARS: GENERAL, RADIO CONTINUUM: GALAXIES, X-RAYS: GALAXIES
Abstract Copyright:
(c) 1998: The American Astronomical Society
Bibliographic Code:
1998ApJ...492...91E

Abstract

We have selected quasars with X-ray colors suggestive of a low-energy cutoff, from the ROSAT Position Sensitive Proportional Counter (PSPC) pointed observations archive. We examine the radio and optical properties of these 13 quasars. Five out of the seven quasars with good optical spectra show associated optical absorption lines, with two having high Delta v candidate systems. Two other cutoff quasars show reddening associated with the quasar. We conclude that absorption is highly likely to be the cause of the X-ray cutoffs, and that the absorbing material is associated with the quasars, not intervening along the line of sight. The suggestion that gigahertz peaked sources are associated with X-ray cutoffs remains unclear with this expanded sample.

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Title:
X-Ray Spectral Survey of WGACAT Quasars. I. Spectral Evolution and Low-Energy Cutoffs
Authors:
Fiore, Fabrizio; Elvis, Martin; Giommi, Paolo; Padovani, Paolo
Journal:
Astrophysical Journal v.492, p.79 (ApJ Homepage)
Publication Date:
01/1998
Origin:
APJ
ApJ Keywords:
GALAXIES: QUASARS: GENERAL, RADIO CONTINUUM: GALAXIES, X-RAYS: GALAXIES
Abstract Copyright:
(c) 1998: The American Astronomical Society
Bibliographic Code:
1998ApJ...492...79F

Abstract

We have used the WGA catalog of ROSAT Position Sensitive Proportional Counter (PSPC) X-ray sources to study the X-ray spectrum of about 500 quasars in the redshift interval 0.1-4.1, detected with a signal-to-noise ratio better than 7. We have parameterized the PSPC spectrum in terms of two "effective energy spectral indices," alpha S (0.1-0.8 keV), and alpha H (0.4-2.4 keV), which allows for the different Galactic NH along the quasars' line of sight. We have used these data to explore the questions raised by the initial PSPC high-redshift quasar studies, and in particular the occurrence of low-energy X-ray cutoffs in high-redshift radio-loud quasars. We have also studied the emission spectra of a large sample of radio-loud and radio-quiet quasars and studied their differences. We find that low-energy X-ray cutoffs are more commonly (and perhaps exclusively) found in radio-loud quasars. Therefore, the low-energy X-ray cutoffs are physically associated with the quasars, and not with intervening systems, since those would affect radio-quiet and radio-loud equally. We suggest that photoelectric absorption is a likely origin of these cutoffs. The number of "cutoffs" in radio-loud quasars significantly increases with redshift rather than with luminosity. A partial correlation analysis confirms that alpha S is truly anticorrelated with redshift at the 99.9% confidence level, indicating evolution with cosmic epoch, and not a luminosity effect. Conversely, for alpha H the observed anticorrelation with redshift is mostly due to a strong dependence on luminosity. In radio-quiet quasars, we find marginal evidence for a flattening of alpha H (P = 4.5%), going from z < 1 to z = 2, in agreement with previous studies. Radio-loud quasars at z < 2.2 instead show a "concave" spectrum ( alpha H < alpha S by ~0.2). This new result is consistent with the widespread suggestion that the flatter X-ray spectra of radio-loud quasars may be due to an additional component above those seen in radio-quiet quasars. However, it might also imply different processes at work in radio-loud and radio-quiet sources. At z >~ 2 the average soft and hard indices are similar and are both significantly smaller than at lower redshifts. This can be due to the soft component of radio-loud quasars being completely shifted out of the PSPC band at z > 2.

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Title:
What can Bepposax Tell us about X-Ray Spectra of BL Lacs?
Authors:
Wolter, A.; Comastri, A.; Ghisellini, G.; Giommi, P.; Guainazzi, M.; Maccacaro, T.; Maraschi, L.; Padovani, P.; Raiteri, C.; Tagliaferri, G.; Urry, C. M.; Villata, M.
Journal:
The Active X-ray Sky: Results from BeppoSAX and RXTE. Proceedings of the Active X-ray Sky symposium, October 21-24, 1997, Rome, Italy, Edited by L. Scarsi, H. Bradt, P. Giommi, and F. Fiore. Publisher: Amsterdam: Elsevier, 1998. Reprinted from: Nuclear Physics B, (Proc. Suppl.), vol. 69/1-3. ISBN: 0444829903., p.411
Publication Date:
00/1998
Origin:
ADS
Bibliographic Code:
1998axrs.symp..411W

Abstract

Not Available

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Title:
A Bepposax Wide Field Camera Secondary Observations Results Database
Authors:
Muller, J. M.; Giommi, P.
Journal:
The Active X-ray Sky: Results from BeppoSAX and RXTE. Proceedings of the Active X-ray Sky symposium, October 21-24, 1997, Rome, Italy, Edited by L. Scarsi, H. Bradt, P. Giommi, and F. Fiore. Publisher: Amsterdam: Elsevier, 1998. Reprinted from: Nuclear Physics B, (Proc. Suppl.), vol. 69/1-3. ISBN: 0444829903., p.622
Publication Date:
00/1998
Origin:
ADS
Bibliographic Code:
1998axrs.symp..622M

Abstract

Not Available

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Title:
The WARPS Blazar Survey
Authors:
Perlman, E. S.; Padovani, P.; Jones, L.; Giommi, P.; Tzioumis, A.; Reynolds, J.; Sambruna, R.
Journal:
New Horizons from Multi-Wavelength Sky Surveys, Proceedings of the 179th Symposium of the International Astronomical Union, held in Baltimore, USA August 26-30, 1996, Kluwer Academic Publishers, edited by Brian J. McLean, Daniel A. Golombek, Jeffrey J. E. Hayes, and Harry E. Payne, p. 310.
Publication Date:
00/1998
Origin:
ADS
Bibliographic Code:
1998IAUS..179..310P

Abstract

Not Available

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Title:
GRB981226 BeppoSAX follow up.
Authors:
Frontera, F.; Montanari, E.; Antonelli, L. A.; Giommi, P.; Daniele, M. R.; Ricci, D.; Coletta, A.; Smith, M.; Tesseri, A.; de Libero, C.; Piro, L.
Journal:
GRB Circular Network, 184, 1 (1998)
Publication Date:
00/1998
Origin:
SIMBAD
Bibliographic Code:
1998GCN...184....1F

Abstract

Not Available

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Title:
The Bepposax Source Catalog
Authors:
Ricci, D.; Fiore, F.; Giommi, P.
Journal:
The Active X-ray Sky: Results from BeppoSAX and RXTE. Proceedings of the Active X-ray Sky symposium, October 21-24, 1997, Rome, Italy, Edited by L. Scarsi, H. Bradt, P. Giommi, and F. Fiore. Publisher: Amsterdam: Elsevier, 1998. Reprinted from: Nuclear Physics B, (Proc. Suppl.), vol. 69/1-3. ISBN: 0444829903., p.618
Publication Date:
00/1998
Origin:
ADS
Bibliographic Code:
1998axrs.symp..618R

Abstract

Not Available

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Title:
The Bepposax Deep Surveys
Authors:
Giommi, P.; Fiore, F.; Ricci, D.; Molendi, S.; Maccarone, M. C.; Comastri, A.
Journal:
The Active X-ray Sky: Results from BeppoSAX and RXTE. Proceedings of the Active X-ray Sky symposium, October 21-24, 1997, Rome, Italy, Edited by L. Scarsi, H. Bradt, P. Giommi, and F. Fiore. Publisher: Amsterdam: Elsevier, 1998. Reprinted from: Nuclear Physics B, (Proc. Suppl.), vol. 69/1-3. ISBN: 0444829903., p.591
Publication Date:
00/1998
Origin:
ADS
Bibliographic Code:
1998axrs.symp..591G

Abstract

Not Available

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Title:
Bepposax Observations of 1 Jy BL Lacertae Objects
Authors:
Padovani, P.; Giommi, P.; Comastri, A.; Ghisellini, G.; Maccacaro, T.; Mantovani, F.; Maraschi, L.; Stanghellini, C.; Tagliaferri, G.; Urry, C. M.; Wolter, A.
Journal:
The Active X-ray Sky: Results from BeppoSAX and RXTE. Proceedings of the Active X-ray Sky symposium, October 21-24, 1997, Rome, Italy, Edited by L. Scarsi, H. Bradt, P. Giommi, and F. Fiore. Publisher: Amsterdam: Elsevier, 1998. Reprinted from: Nuclear Physics B, (Proc. Suppl.), vol. 69/1-3. ISBN: 0444829903., p.431
Publication Date:
00/1998
Origin:
ADS
Bibliographic Code:
1998axrs.symp..431P

Abstract

Not Available

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Title:
X-Ray Luminosity and Spectral Variability in the Tev BL Lac 1ES2344+514
Authors:
Giommi, P.; Padovani, P.; Perlman, E.
Journal:
The Active X-ray Sky: Results from BeppoSAX and RXTE. Proceedings of the Active X-ray Sky symposium, October 21-24, 1997, Rome, Italy, Edited by L. Scarsi, H. Bradt, P. Giommi, and F. Fiore. Publisher: Amsterdam: Elsevier, 1998. Reprinted from: Nuclear Physics B, (Proc. Suppl.), vol. 69/1-3. ISBN: 0444829903., p.407
Publication Date:
00/1998
Origin:
ADS
Bibliographic Code:
1998axrs.symp..407G

Abstract

Not Available

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Title:
The active X-ray sky: results from BeppoSAX and RXTE
Authors:
Scarsi, L.; Bradt, H.; Giommi, P.; Fiore, F.
Journal:
The active X-ray sky: results from BeppoSAX and RXTE. Proceedings of the Active X-ray Sky symposium, October 21-24, 1997, Rome, Italy, Edited by L. Scarsi, H. Bradt, P. Giommi, and F. Fiore. Publisher: Amsterdam: Elsevier, 1998. Reprinted from: Nuclear Physics B, (Proc. Suppl.), vol. 69/1-3. ISBN: 0444829903
Publication Date:
00/1998
Origin:
ESO; ELSEVIER
Keywords:
X RAY ASTRONOMY, ARTIFICIAL SATELLITES, CONFERENCES
Bibliographic Code:
1998axrs.symp.....S

Abstract

The conference on Active X-Ray Sky was held approximately two years after the la unch of the Rossi-Xte and RXTE satellites. The objective of these proceedings was to incorporate results not only from these two missions, but to review recent developments about the Active X-ray Sky as obtained from the four currectly active X-ray missions, as well as from the Copton Gamma-ray Observatory. Some of the very dramatic findings were: the discovery of X-ray and optical afterglow in Gamma Ray Bursts; the discovery of X-ray oscillations at kilohertz frequencies from binary systems and the discovery of correlated IR flares, radio flares and X-ray dip-flare cycles in microquasars. These results have yielded dramatic new insights into our physical universe. Other important results reported or reviewed here include the detection of extreme high-energy emission in the active binary stars Algol and UX Ari, resonant absorption scattering from the Perseus Cluster, and cyclotron lines from pulsars. These and many other recent and important results are published here, resulting in a state-of-art review by experts currently active in the field.

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Title:
First Results from a Systematic Search for New X-Ray Pulsators in ROSAT PSPC Fields
Authors:
Israel, G. L.; Treves, A.; Stella, L.; Angelini, L.; White, N. E.; Kallman, T.; Covino, S.; Giommi, P.
Journal:
The Many Faces of Neutron Stars. Edited by R. Buccheri, J. van Paradijs, and M. A. Alpar. Dordrecht ; Boston : Kluwer Academic Publishers, 1998., p.411
Publication Date:
00/1998
Origin:
ADS
Bibliographic Code:
1998mfns.conf..411I

Abstract

Not Available

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Title:
XTE J0053-724
Authors:
Buckley, D. A. H.; Coe, M. J.; Stevens, J. B.; Angelini, L.; White, N. E.; Giommi, P.
Journal:
IAU Circ., 6789, 2 (1997). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
12/1997
Origin:
CBAT
Objects:
XTE J0053-724
Bibliographic Code:
1997IAUC.6789....2B

Abstract

IAUC 6789 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
X-raying a galaxy - PHL 6625 behind NGC 247
Authors:
Elvis, Martin; Fiore, Fabrizio; Giommi, Paolo; Padovani, Paolo
Affiliation:
AA(Harvard-Smithsonian Center for Astrophysics), AB(Roma, Osservatorio Astronomico), AC(BeppoSAX Science Data Center), AD(Roma II, Univ.)
Journal:
Royal Astronomical Society, Monthly Notices, vol. 291, p. L49-L52 (MNRAS Homepage)
Publication Date:
11/1997
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
QUASARS, ACTIVE GALACTIC NUCLEI, INTERSTELLAR MATTER, X RAY SOURCES, ABSORPTION SPECTRA, X RAY SPECTRA, H I REGIONS, HIGH SPEED
Bibliographic Code:
1997MNRAS.291L..49E

Abstract

PHL 6625, a z = 0.38, radio-quiet quasar, shows a clear excess of low-energy absorption in its ROSAT PSPC soft X-ray spectrum. This absorption is almost certainly produced by the ISM in NGC 247, a foreground spiral galaxy, which lies about 3.4 kpc (4.6 arcmin) away in projection. Comparison of the X-ray absorption and the 21-cm H I column density through NGC 247 suggests a larger than expected effect in X-rays. Several possibilities are considered to explain this apparent discrepancy. Additional high-velocity H I components of the ISM are currently the most plausible cause. PHL 6625 also clearly decreased in its soft X-ray flux by a factor of two in six months.

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Title:
The Discovery of 8.9 Second Pulsations from the Variable X-Ray Source 2E 0050.1-7247 in the Small Magellanic Cloud
Authors:
Israel, G. L.; Stella, L.; Angelini, L.; White, N. E.; Giommi, P.; Covino, S.
Journal:
Astrophysical Journal Letters v.484, p.L141 (ApJ Homepage)
Publication Date:
08/1997
Origin:
APJ
ApJ Keywords:
STARS: BINARIES: GENERAL, STARS: EMISSION-LINE, BE, STARS: PULSARS: INDIVIDUAL ALPHANUMERIC: 2E 0050.1-, 247, STARS: ROTATION, X-RAYS: STARS
Abstract Copyright:
(c) 1997: The American Astronomical Society
Bibliographic Code:
1997ApJ...484L.141I

Abstract

During a systematic search for periodic signals in a sample of ROSAT PSPC light curves, we discovered ~8.9 s X-ray pulsations in 2E 0050.1-7247, a variable X-ray source in the Small Magellanic Cloud. The source was detected several times between 1979 and 1993 at luminosity levels ranging from ~5 x 1034 ergs s-1 up to 1.4 x 1036 ergs s-1 with both the Einstein IPC and ROSAT PSPC. The X-ray energy spectrum is consistent with a power-law spectrum that steepens as the source luminosity decreases. We revealed a pronounced H alpha activity from at least two B stars in the X-ray error circles. These results strongly suggest that the X-ray pulsar 2E 0050.1-7247 is in a Be-type massive binary.

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Title:
GRB 970508
Authors:
Piro, L.; Costa, E.; Feroci, M.; Soffitta, P.; Antonelli, L. A.; Fiore, F.; Giommi, P.; Owens, A.; Parmar, A.; Molendi, S.; Cusumano, G.; in 't Zand, J.; Heise, J.; Frontera, F.; Zavattini, G.; Nicastro, L.; Palazzi, E.; Smith, M.; Gandolfi, G.; Torroni, V.; Spoliti, G.; Coletta, A.; Capalbi, M.; Rebecchi, S.; Ricci, D.; Bruca, L.; Crisigiovanni, G.; Salotti, L.; Gennaro, G.; Delibero, C.; Butler, R. C.; Jaunsen, A. O.; Grav, T.; Oestensen, R.; Pedersen, H.
Journal:
IAU Circ., 6656, 1 (1997). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
05/1997
Origin:
CBAT
Objects:
GRB 970508
Bibliographic Code:
1997IAUC.6656....1P

Abstract

IAUC 6656 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
GS 1826-238
Authors:
Ubertini, P.; Bazzano, A.; Cocchi, M.; Natalucci, L.; Heise, J.; Jager, R.; in 't Zand, J.; Muller, J. M.; Smith, M.; Celidonio, G.; Coletta, A.; Ricci, R.; Giommi, P.; Ricci, D.; Capalbi, M.; Menna, M. T.; Rebecchi, S.
Journal:
IAU Circ., 6611, 1 (1997). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
04/1997
Origin:
CBAT
Objects:
GS 1826-238
Bibliographic Code:
1997IAUC.6611....1U

Abstract

IAUC 6611 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
GRB 970402
Authors:
Piro, L.; Feroci, M.; Costa, E.; Antonelli, L. A.; Fiore, F.; Giommi, P.; Owens, A.; Parmar, A.; Molendi, S.; Cusumano, G.; in 't Zand, J.; Heise, J.; Jager, R.; Frontera, F.; Zavattini, G.; Nicastro, L.; Palazzi, E.; Salotti, L.; di Ciolo, L.; D'Andreta, G.; Ricci, R.; Spoliti, G.; Coletta, A.; Capalbi, M.; Daniele, M. R.; Butler, R. C.
Journal:
IAU Circ., 6617, 1 (1997). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
04/1997
Origin:
CBAT
Objects:
GRB 970402
Bibliographic Code:
1997IAUC.6617....1P

Abstract

IAUC 6617 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
SAX J1750.8-2900
Authors:
Bazzano, A.; Heise, J.; Ubertini, P.; Cocchi, M.; Natalucci, L.; Muller, J. M.; Jager, R.; in 't Zand, J.; di Ciolo, L.; Celidonio, G.; Coletta, A.; Giommi, P.; Ricci, D.; Capalbi, M.; Rebecchi, S.
Journal:
IAU Circ., 6597, 1 (1997). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
03/1997
Origin:
CBAT
Objects:
SAX J1750.8-2900
Bibliographic Code:
1997IAUC.6597....1B

Abstract

IAUC 6597 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
GRB 970228
Authors:
Costa, E.; Feroci, M.; Piro, L.; Cinti, M. N.; Frontera, F.; Zavattini, G.; Nicastro, L.; Palazzi, E.; dal Fiume, D.; Orlandini, M.; in 't Zand, J.; Heise, J.; Jager, R.; Parmar, A.; Owens, A.; Molendi, S.; Cusumano, G.; Maccarone, M. C.; Giarrusso, S.; Antonelli, L. A.; Fiore, F.; Giommi, P.; Muller, J. M.; Salotti, L.; Gennaro, G.; Stornelli, M.; Crisigiovanni, G.; Ricci, R.; Coletta, A.; Butler, R. C.; Frail, D. A.; Kulkarni, S. R.
Journal:
IAU Circ., 6576, 1 (1997). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
03/1997
Origin:
CBAT
Objects:
GRB 970228
Bibliographic Code:
1997IAUC.6576....1C

Abstract

IAUC 6576 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
GRB 960720
Authors:
Greiner, J.; Heise, J.; Piro, L.; Costa, E.; Feroci, M.; Cinti, M.; Frontera, F.; dal Fiume, D.; Nicastro, L.; Orlandini, M.; Pizzichini, G.; Jager, R.; Fiore, F.; Giommi, P.; Antonelli, A.; Muller, J. M.; Parmar, A.; Maccarone, M. C.; Chiappetti, L.; Butler, R. C.
Journal:
IAU Circ., 6570, 1 (1997). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
03/1997
Origin:
CBAT
Objects:
GRB 960720
Bibliographic Code:
1997IAUC.6570....1G

Abstract

IAUC 6570 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
BY Draconis
Authors:
Mewe, R.; Heise, J.; Muller, J. M.; Coletta, A.; D'Andreta, G.; di Ciolo, L.; Spoliti, G.; Ricci, R.; Giommi, P.; Piro, L.
Journal:
IAU Circ., 6551, 2 (1997). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
02/1997
Origin:
CBAT
Objects:
BY Dra
Bibliographic Code:
1997IAUC.6551....2M

Abstract

IAUC 6551 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
The Discovery of 13 Second X-Ray Pulsations from the Hydrogen-depleted Subdwarf O6 Star Binary HD 49798
Authors:
Israel, G. L.; Stella, L.; Angelini, L.; White, N. E.; Kallman, T. R.; Giommi, P.; Treves, A.
Journal:
Astrophysical Journal Letters v.474, p.L53 (ApJ Homepage)
Publication Date:
01/1997
Origin:
APJ
ApJ Keywords:
STARS: BINARIES: SPECTROSCOPIC, STARS: PULSARS: INDIVIDUAL ALPHANUMERIC: HD 49798, STARS: ROTATION, STARS: SUBDWARFS, X-RAYS: STARS
Abstract Copyright:
(c) 1997: The American Astronomical Society
Bibliographic Code:
1997ApJ...474L..53I

Abstract

We have discovered strong ~13 s X-ray pulsations in the ROSAT Position Sensitive Proportional Counter light curve of HD 49798, a 1.55 day single-component spectroscopic binary containing a hydrogen-depleted subdwarf O6 star. We find no evidence for period changes during the ~4 hr ROSAT pointing. The source X-ray spectrum is extremely soft, with an unabsorbed 0.1--2 keV luminosity of a few times 1032 ergs s-1 (distance of 650 pc). A higher luminosity might be hidden in the EUV. Our results imply that the unseen companion is an accreting degenerate star, a white dwarf, or, more likely, a neutron star. In any case, HD 49798 corresponds to a previously unobserved evolutionary stage of a massive binary system after the common-envelope phase and spiraling in.

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Title:
Are the X-ray spectra of flat-spectrum radio quasars and BL Lacertae objects different?
Authors:
Padovani, Paolo; Giommi, Paolo; Fiore, Fabrizio
Affiliation:
AA(Dipartimento di Fisica, II Universita di Roma `Tor Vergata', Via della Ricerca Scientifica 1, I-00133 Roma, Italy ), AB(SAX, Science Data Center, ASI, Viale Regina Margherita 202, I-00198 Roma, Italy ), AC(SAX, Science Data Center, ASI, Viale Regina Margherita 202, I-00198 Roma, Italy )
Journal:
Monthly Notices of the Royal Astronomical Society, Volume 284, Issue 3, pp. 569-575. (MNRAS Homepage)
Publication Date:
01/1997
Origin:
MNRAS
MNRAS Keywords:
GALAXIES, ACTIVE - BL LACERTAE OBJECTS, GENERAL - QUASARS, GENERAL - RADIO CONTINUUM, GALAXIES - X-RAYS, GALAXIES
Abstract Copyright:
(c) 1997 The Royal Astronomical Society
Bibliographic Code:
1997MNRAS.284..569P

Abstract

We study the X-ray spectra of 114 flat-spectrum radio quasars (FSRQ) using the hardness ratios as given in the WGA catalogue of ROSAT sources. This sample includes all WGA FSRQ with high-quality data and comprises about 20 per cent of presently known such objects, which makes this the largest FSRQ sample ever studied in the X-ray band. We find that FSRQ have a distribution of energy spectral indices ranging between 0 and 3 with a mean value alpha_x~1. This is consistent with that of low-energy cut-off BL Lacs (LBL; alpha_x~1.1), generally found in radio surveys, but significantly different from that of high-energy cut-off BL Lacs (HBL), normally selected in the X-ray band, which display steeper X-ray spectra (alpha_x~1.5). The shape of the optical-to-X-ray continuum is concave (that is, alpha_x<alpha_ox) for the majority of FSRQ, as found for LBL, supporting a dominance of inverse Compton emission in the X-ray band in most objects. Our results are at odds with previous studies of the X-ray spectra of FSRQ, which were, however, plagued by low spectral resolution and/or small-number statistics and selection effects, and have important implications for the proposed connections between FSRQ and BL Lacs.

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Title:
A pilot study for the creation of a large BL Lac sample
Authors:
Wolter, A.; Ciliegi, P.; della Ceca, R.; Gioia, I. M.; Giommi, P.; Henry, J. P.; Maccacaro, T.; Padovani, P.; Ruscica, C.
Affiliation:
AA(Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy ), AB(Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy ), AC(Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy ), AD(Istituto di Radio Astronomia del CNR, via Gobetti 101, 40129 Bologna, Italy ), AE(SAX Science Data Center, ASI, Viale Regina Margherita 202, I-00198 Rome, Italy ), AF(Institute for Astronomy, 2680 Woodlawn Dr., Honolulu, HI 96822, USA ), AG(Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy ), AH(Dipartimento di Fisica, Il Universita di Roma `Tor Vergata', Via della Ricerca Scientifica 1, 00133 Roma, Italy ), AI(Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy )
Journal:
Monthly Notices of the Royal Astronomical Society, Volume 284, Issue 1, pp. 225-234. (MNRAS Homepage)
Publication Date:
01/1997
Origin:
MNRAS
MNRAS Keywords:
BL LACERTAE OBJECTS: GENERAL, RADIO CONTINUUM: GALAXIES, X-RAYS: GALAXIES
Abstract Copyright:
(c) 1997 The Royal Astronomical Society
Bibliographic Code:
1997MNRAS.284..225W

Abstract

We discuss a new method for finding BL Lac objects based on their multifrequency properties. BL Lacs are both X-ray and radio loud, thus a programme aimed at the optical identification of radio emitting X-ray (REX) sources has the potential of being highly efficient (expected success rate of ~20-30 per cent) in finding them. Here we present the results of a pilot study in which 17 REX have been obtained from the cross-correlation of X-ray sources from 35 PSPC images with a 6-cm radio catalogue. Eleven sources have been identified, either through optical spectra obtained by us (6 sources) or by a search in the literature (5 sources), with a success rate of 2/11. We intend to pursue a systematic search for BL Lac objects, exploiting all the available and suitable PSPC data and radio catalogues. Our goal is to create a sample of more than 100 BL Lac objects at an X-ray flux limit of ~5x10^-14 erg cm^-2 s^-1. This sample will allow us to fill the parameter space of the BL Lac population in a more extended way than previously possible and, therefore, to check more thoroughly the relation between statistical and physical properties of this class of objects.

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Title:
Discovery of an X-ray afterglow associated with the gamma-ray burst of 28 February 1997.
Authors:
Costa, E.; Frontera, F.; Heise, J.; Feroci, M.; in 't Zand, J.; Fiore, F.; Cinti, M. N.; dal Fiume, D.; Nicastro, L.; Orlandini, M.; Palazzi, E.; Rapisarda, M.; Zavattini, G.; Jager, R.; Parmar, A.; Owens, A.; Molendi, S.; Cusumano, G.; Maccarone, M. C.; Giarrusso, S.; Coletta, A.; Antonelli, L. A.; Giommi, P.; Muller, J. M.; Piro, L.; Butler, R. C.
Journal:
Nature, 387, 783-785 (1997)
Publication Date:
00/1997
Origin:
SIMBAD
Bibliographic Code:
1997Natur.387..783C

Abstract

Not Available

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Title:
A multifrequency database of active galactic nuclei:
Authors:
Padovani, P.; Giommi, P.; Fiore, F.
Journal:
Memorie della Societa Astronomia Italiana, Vol. 68, p.147
Publication Date:
00/1997
Origin:
OCR
Bibliographic Code:
1997MmSAI..68..147P

Abstract

Not Available.

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Title:
Associated Absorption at Low and High Redshift.
Authors:
Elvis, M.; Mathur, S.; Wilkes, B. J.; Fiore, F.; Giommi, P.; Padovani, P.
Journal:
In Emission Lines in Active Galaxies: New Methods and Techniques, Proceedings of IAU Colloquium No. 159, Astronomical Society of the Pacific Conference Series, vol. 113, eds. B. M. Peterson, F. Z. Cheng, and A. S. Wilson, p. 236. San Francisco: Astronomical Society of the Pacific, 1997.
Publication Date:
00/1997
Origin:
SAO
Bibliographic Code:
1997elag.conf..236E

Abstract

Not Available

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Title:
The BeppoSAX WWW Catalog Browser
Authors:
Giommi, P.; Antonelli, L. A.; Fiore, F.; Matteuzzi, A.; Signorile, S.
Journal:
Data Analysis in Astronomy, Proceedings of the Fifth Workshop. Ettore Majorana Centre for Scientific Culture, Erice, Italy. 27 Oct - 3 Nov, 1996. Edited by V. Di Gesu, M. J. B. Duff, A. Heck, M. C. Maccarone, L. Scarsi and H. U. Zimmerman. World Scientific Press, 1997., p.151
Publication Date:
00/1997
Origin:
ADS
Bibliographic Code:
1997daia.conf..151G

Abstract

Not Available

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Title:
The BeppoSAX Science Data Center
Authors:
Giommi, P.; Fiore, F.
Journal:
Data Analysis in Astronomy, Proceedings of the Fifth Workshop. Ettore Majorana Centre for Scientific Culture, Erice, Italy. 27 Oct - 3 Nov, 1996. Edited by V. Di Gesu, M. J. B. Duff, A. Heck, M. C. Maccarone, L. Scarsi and H. U. Zimmerman. World Scientific Press, 1997., p.93
Publication Date:
00/1997
Origin:
ADS
Bibliographic Code:
1997daia.conf...93G

Abstract

Not Available

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Title:
Initial Results from the High Energy Experiment PDS Aboard BeppoSAX
Authors:
Frontera, F.; dal Fiume, D.; Costa, E.; Feroci, M.; Orlandini, M.; Nicastro, L.; Palazzi, E.; Zavattini, G.; Giommi, P.
Journal:
Proceedings of the Fourth Compton Symposium, Editors Charles D. Dermer, Mark S. Strickman, and James D. Kurfess, Williamsburg, VA April 1997: AIP Conference Proceedings 410, p. 1493. (CoMP Homepage)
Publication Date:
00/1997
Origin:
ADS
Bibliographic Code:
1997comp.symp.1493F

Abstract

Not Available

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Title:
BeppoSAX Monitoring of the BL Lac MKN 501
Authors:
Pian, E.; Vacanti, G.; Tagliaferri, G.; Ghisellini, G.; Maraschi, L.; Treves, A.; Urry, C. M.; Fiore, F.; Giommi, P.; Palazzi, E.; Chiappetti, L.; Sambruna, R. M.
Journal:
Proceedings of the Fourth Compton Symposium, Editors Charles D. Dermer, Mark S. Strickman, and James D. Kurfess, Williamsburg, VA April 1997: AIP Conference Proceedings 410, p. 1412. (CoMP Homepage)
Publication Date:
00/1997
Origin:
ADS
Bibliographic Code:
1997comp.symp.1412P

Abstract

Not Available

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Title:
The ROSAT WGACAT Variable Sources
Authors:
White, N. E.; Angelini, L.; Giommi, P.
Affiliation:
AA(LHEA/GSFC) AB(LHEA/GSFC) AC(SSDC)
Journal:
"All-Sky X-Ray Observations in the Next Decade", 1997, RIKEN, Japan, eds. M. Matsuoka and N. Kawai, p. 41.
Publication Date:
00/1997
Origin:
AUTHOR
Bibliographic Code:
1997asxo.proc...41W

Abstract

The WGACAT is an X-ray catalog of point sources generated using 3310 ROSAT PSPC sequences taken from the HEASARC public archives. The catalog contains in excess of 68,000 detections, with more than 62,000 individual sources. The data processing included a method for detecting variable sources. This used a KS test where the photon arrival time distribution for a given source was compared to that of the photons in the remainder of the field. The resulting chi2 value for each source was used to find highly variable sources. A total of 216 new variable sources were detected. The typical variability is a flare-like light curve with a risetime of 5,000s and a decay of 30,000s. Of the 216 variable sources only 30% have an ID with a previously cataloged object. The vast majority of these are stars, with the remainder AM Her objects, QSOs, sources in the SMC and M31. We discuss the implications of this time variability survey for future more sensitive ASM detectors, and predict the likely frequency of variability at a given flux level.

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Title:
The WGACAT version of ROSAT sources (White+ 1995)
Authors:
White, N. E.; Giommi, P.; Angelini, L.
Journal:
VizieR On-line Data Catalog: IX/12. Originally published in: HEASARC, Code 660, LHEA/GSFC, Greenbelt (1995)
Publication Date:
10/1996
Origin:
SIMBAD
Keywords:
X-ray sources
Comment:
Obsoleted by IX/31
Bibliographic Code:
1996yCat.9012....0W

Abstract

WGACAT is a catalogue of point sources generated at HEASARC from all the ROSAT PSPC (Position Sensitive Proportional Counter) pointing observations from Feb 1991 to March 1994. These were the files available in the public archive at HEASARC as of September 1994. This catalog is an independent research effort aimed at releasing as quickly as possible a list of sources detected by ROSAT in its pointed phase to: (1) identify the detected sources, (2) ensure their timely observation by currently active X-ray missions e.g. ASCA, (3) to search for objects which show exceptional time variability and spectral properties and (4) to provide an independent check of the detection technique used in the official ROSAT project (SAS) processing. WGACAT stands for N.E. White (HEASARC/GSFC). P. Giommi (ESA), and L. Angelini (HEASARC/GSFC) (1 data file).

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Title:
GRB 960720
Authors:
Piro, L.; Costa, E.; Feroci, M.; Cinti, M.; Frontera, F.; dal Fiume, D.; Nicastro, L.; Orlandini, M.; Pizzichini, G.; Heise, J.; Jager, R.; Fiore, F.; Giommi, P.; Matteuzzi, A.; Muller, H.; Parmar, A.; Sacco, B.; Molendi, S.; Butler, R. C.
Journal:
IAU Circ., 6480, 1 (1996). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
09/1996
Origin:
CBAT
Objects:
GRB 960720
Bibliographic Code:
1996IAUC.6480....1P

Abstract

IAUC 6480 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
Cygnus X-1
Authors:
Piro, L.; Butler, R. C.; Boella, G.; Scarsi, L.; Bleeker, J. A. M.; Parmar, A.; Chiappetti, L.; Sacco, B.; Giarrusso, S.; Santangelo, A.; Frontera, F.; dal Fiume, D.; Costa, E.; Jager, R.; Heise, J.; Giommi, P.
Journal:
IAU Circ., 6431, 1 (1996). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
07/1996
Origin:
CBAT
Objects:
Cyg X-1
Bibliographic Code:
1996IAUC.6431....1P

Abstract

IAUC 6431 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
A catalogue of BL Lacertae objects (Padovani+ 1995)
Authors:
Padovani, P.; Giommi, P.
Journal:
VizieR On-line Data Catalog: J/MNRAS/277/1477. Originally published in: 1995MNRAS.277.1477P
Publication Date:
03/1996
Origin:
SIMBAD
Keywords:
BL Lac objects, X-ray sources, Radio sources
Bibliographic Code:
1996yCat..72771477P

Abstract

We present a catalogue of 233 BL Lacertae objects compiled through an extensive bibliographic search updated to mid-1995. A large fraction of the sources listed in the catalogue belongs to well-defined samples and can be used for statistical purposes. A smaller fraction consists of miscellaneous (but confirmed) BL Lacs and of objects classified as BL Lac candidates. We discuss the selection criteria of the different samples, report the discovery of two previously unnoticed BL Lacs in the Palomar-Green survey, and comment on the possible association of some of the still unidentified high galactic latitude gamma-ray (EGRET, see Thompson et al., =1995ApJS..101..259T) sources with BL Lacs. Some statistical properties of the catalogue are also briefly discussed. (1 data file).

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Title:
The ROSAT X-ray spectra of BL Lacertae objects
Authors:
Padovani, Paolo; Giommi, Paolo
Affiliation:
AA(Dipartimento di Fisica, II Universita di Roma `Tor Vergata', Via della Ricerca Scientifica 1, I-00133 Roma, Italy ), AB(SAX, Scientific Data Center, ASI, Viale Regina Margherita 202, I-00198 Roma, Italy )
Journal:
Monthly Notices of the Royal Astronomical Society, Volume 279, Issue 2, pp. 526-534. (MNRAS Homepage)
Publication Date:
03/1996
Origin:
MNRAS
MNRAS Keywords:
GALAXIES: ACTIVE, BL LACERTAE OBJECTS: GENERAL, X-RAYS: GALAXIES
Abstract Copyright:
(c) 1996 The Royal Astronomical Society
Bibliographic Code:
1996MNRAS.279..526P

Abstract

We study the X-ray spectra of 85 BL Lacertae objects using the hardness ratios as given in the White, Giommi & Angelini (WGA) catalogue of ROSAT sources. This sample includes all WGA BL Lacs with high-quality data and comprises about 50 per cent of presently known BL Lacs. We find that BL Lacs have energy power-law spectral indices between 0 and 3 with a mean value alpha_x~1.4. Significant differences, however, are present between high-energy cut-off BL Lacs (HBLs), normally selected in the X-ray band, and low-energy cut-off BL Lacs (LBLs), generally found in radio surveys. HBLs have steeper X-ray spectral slopes (alpha_x~1.5) well correlated with alpha_ox, and anti-correlated with the X-ray-to-radio flux and cut-off frequency, with convex overall broad-band spectra. LBLs, on the other hand, have flatter X-ray spectra (alpha_x~1.1) and concave optical-X-ray continuum. We interpret these results in terms of different mechanisms being responsible for the X-ray emission in the two classes, namely, synchrotron and inverse Compton for HBLs and LBLs, respectively. The observed differences are consistent with the hypothesis that HBLs and LBLs are powered by essentially the same non-thermal engines differing mainly in their synchrotron cut-off energy.

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Title:
The ROSAT variable Sky
Authors:
Angelini, L.; Giommi, P.; White, N. E.
Journal:
Proc. 'Röntgenstrahlung from the Universe', eds. Zimmermann, H.U.; Trümper, J.; and Yorke, H.; MPE Report 263, p. 645-646
Publication Date:
02/1996
Origin:
MPE
Bibliographic Code:
1996rftu.proc..645A

Abstract

Not Available

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Title:
The ROSAT X-Ray Spectra of BL Lacertae Objects
Authors:
Padovani, P.; Giommi, P.
Journal:
Extragalactic radio sources: proceedings of the 175th Symposium of the International Astronomical Union, held in Bologna, Italy, 10-14 October 1995. Edited by Ron D. Ekers, C. Fanti, and L. Padrielli. Published by Kluwer Academic Publishers, p. 267.
Publication Date:
00/1996
Origin:
ADS
Bibliographic Code:
1996IAUS..175..267P

Abstract

Not Available

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Title:
A Sample-Oriented Catalogue of Bl-Lacertae Objects
Authors:
Padovani, P.; Giommi, P.
Journal:
R.A.S. MONTHLY NOTICES V.277, NO. 4/DEC15, P.1477, 1995 (MNRAS Homepage)
Publication Date:
12/1995
Origin:
KNUDSEN; NED
Bibliographic Code:
1995MNRAS.277.1477P

Abstract

We present a catalogue of 233 BL Lacertae objects compiled through an extensive bibliographic search updated to mid-1995. A large fraction of the sources listed in the catalogue belongs to well-defined samples and can be used for statistical purposes. A smaller fraction consists of miscellaneous (but confirmed) BL Lacs and of objects classified as BL Lac candidates. We discuss the selection criteria of the different samples, report the discovery of two previously unnoticed BL Lacs in the Palomar-Green survey, and comment on the possible association of some of the still unidentified high galactic latitude gamma-ray (EGRET) sources with BL Lacs. Some statistical properties of the catalogue are also briefly discussed.

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Title:
HD 49798 and 2E 0050.1-7247
Authors:
Israel, G. L.; Stella, L.; Angelini, L.; White, N. E.; Giommi, P.
Journal:
IAU Circ., 6277, 1 (1995). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
12/1995
Origin:
CBAT
Objects:
HD 49798; 2E 0050.1-7247
Bibliographic Code:
1995IAUC.6277....1I

Abstract

IAUC 6277 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
The Softest X-Ray Sources in the ROSAT Pointed Catalog: WGACAT
Authors:
Singh, K. P.; Barrett, P.; White, N. E.; Giommi, P.; Angelini, L.
Journal:
Astrophysical Journal v.455, p.456 (ApJ Homepage)
Publication Date:
12/1995
Origin:
APJ; KNUDSEN
ApJ Keywords:
GALAXIES: ACTIVE, STARS: NOVAE, CATACLYSMIC VARIABLES, STARS: WHITE DWARFS, X-RAYS: STARS
Bibliographic Code:
1995ApJ...455..456S

Abstract

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Title:
The X-Ray Spectra of Blazars: Analysis of the Complete EXOSAT Archive: Erratum
Authors:
Sambruna, Rita M.; Barr, Paul; Giommi, Paolo; Maraschi, Laura; Tagliaferri, Gianpiero; Treves, Aldo
Journal:
Astrophysical Journal Supplement v.99, p.295 (ApJS Homepage)
Publication Date:
07/1995
Origin:
APJ; KNUDSEN; NED
ApJ Keywords:
ERRATA, ADDENDA
Bibliographic Code:
1995ApJS...99..295S

Abstract

In the paper "The X-Ray Spectra of Blazars: Analysis of the Complete EXOSAT Archive" by Rita M. Sambruna, Paul Barr, Paolo Giommi, Laura Maraschi, Gianpiero Tagliaferri, and Aldo Treves (ApJS, 95,371 [1994]), the section regarding the object PKS 1510-08 (Section 4.4.14) contains an erroneous quotation. K. P. Singh, A.R. Rao, and M.N. Vahia (ApJ, 365,455 [1990]) in fact detected: emission line only in the 1984 data, and not in the 1985 spectrum, as stated.

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Title:
RX J0045.4+4154: A recurrent supersoft x-ray transient in M31
Authors:
White, N. E.; Giommi, P.; Heise, J.; Angelini, L.; Fantasia, S.
Affiliation:
AA(NASA Goddard Space Flight Center, Greenbelt, Maryland, US), AB(NASA Goddard Space Flight Center, Greenbelt, Maryland, US), AC(NASA Goddard Space Flight Center, Greenbelt, Maryland, US), AD(NASA Goddard Space Flight Center, Greenbelt, Maryland, US), AE(NASA Goddard Space Flight Center, Greenbelt, Maryland, US)
Journal:
Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 445, no. 2, p. L125-L128 (ApJ Homepage)
Publication Date:
06/1995
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
EMISSION SPECTRA, NOVAE, STELLAR ACTIVITY, STELLAR TEMPERATURE, WHITE DWARF STARS, X RAY ASTRONOMY, X RAY SPECTRA, X RAY STARS, DENSITY (NUMBER/VOLUME), HYDROGEN, ROSAT MISSION, STELLAR LUMINOSITY
Bibliographic Code:
1995ApJ...445L.125W

Abstract

Using data extracted from the ROSAT archive we have discovered a recurrent supersoft X-ray transient RX J0045.4+4154 in M31. The first outburst began on 1992 February 2 and continued for at least 4 days, until the end of the observation sequence. A second outburst that lasted more than 6 days was seen to begin on 1993 January 7. The X-ray spectrum on both occasions yields a characteristic blackbody temperature of approximately 90 eV. For a range of plausible continuum models, the hydrogen column density is (0.8-1.5) x 1021/sq cm and is consistent with the source being located in M31. This implies an unabsorbed 0.1-2.0 keV peak luminosity of approximately 1038 ergs/sec. This is the first recurrent X-ray transient to be found in M31 and is particularly notable because it is much softer than the bright X-ray transients seen in our Galaxy. The spectrum is characteristic of the supersoft class of X-ray sources, which are thought to be accreting white dwarfs that have a hydrogen-burning surface layer. A fit to a white dwarf model atmosphere gives a temperature of 106K, the hottest found so far. This high temperature is consistent with a white dwarf mass of 1.3-1.4 solar mass, approaching the Chandrasekhar limit, and burning close to the nuclear stability limit.

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Title:
The connection between x-ray- and radio-selected BL Lacertae objects
Authors:
Padovani, Paolo; Giommi, Paolo
Affiliation:
AA(Universita di Roma, Roma, Italy), AB(Universita di Roma, Roma, Italy)
Journal:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 444, no. 2, p. 567-581 (ApJ Homepage)
Publication Date:
05/1995
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
BL LACERTAE OBJECTS, OPTICAL PROPERTIES, RADIO ASTRONOMY, SPECTRUM ANALYSIS, X RAY ASTRONOMY, EMISSION SPECTRA, ENERGY SPECTRA, HEAO 2, LUMINOSITY, RED SHIFT, SPATIAL DISTRIBUTION
Bibliographic Code:
1995ApJ...444..567P

Abstract

We explain the properties of X-ray-selected BL Lacertae objects, under the assumption that they constitute the small minority of the BL Lac population with energy cutoff located in the UV/X-ray band, as suggested by their multifrequency spectra. In particular, we derive their X-ray luminosity funcion, log N-log S, and radio flux distribution starting rom radio-selected BL Lac objects using a method that does not require any free parameters. Our hypothesis is at variance with the most common explanation for the existence of two clases of BL Lac objects, namely, that X-ray-selected objects are viewed significantly off the beaming axis while radio-selected ones have their jets more aligned with the line of sight. In this case, in fact, X-ray-selected sources should be intrinsically more numerous than objects selected in the radio band at a fixed value of some isotropic luminosity such as tha of the diffuse radio emission. While also accounting for most of the properties of BL Lac objects detected in current X-ray surveys, this latter scenario would predict their radio emission to be dominated by the extended unbeamed component, in contrast with observations. We also address the question of the negative evolution apparently exhibited by X-ray-selected BL Lac objects, showing that neither recognition problems nor a break in the X-ray spectrum are likely to be responsible for it. Our hypothesis explains in a simple way the bimodal distribution of BL Lac objects in the alpharo - alphaox diagarm. It also makes specific predictions for the X-ray, radio, and optical properties of BL Lac objects which will be tested by future deep X-ray surveys.

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Title:
Radio to X-Ray distribution of BL Lac Objects (Giommi+, 1995)
Authors:
Giommi, P.; Ansari, S. G.; Micol, A.
Journal:
VizieR On-line Data Catalog: J/A+AS/109/267. Originally published in: 1995A&AS..109..267G
Publication Date:
02/1995
Origin:
SIMBAD
Keywords:
BL Lac objects, Radio sources, X-ray sources IPC Slew Survey and EXOSAT HGLS
Bibliographic Code:
1995yCat..41090267G

Abstract

We present multifrequency spectra of a large number of radio and X-ray selected BL Lacertae objects constructed using non-simultaneous archival data. The data were obtained using the European Space Information System (ESIS) and are from several radio and optical catalogues, the IRAS Faint Source Catalogue, the Einstein and the EXOSAT databases. The sample includes 121 BL Lacs that have been extracted from the 1Jy (1991ApJ...374..431S) and the S4 (1994A&AS..103..349S) radio surveys, the Einstein IPC Slew Survey, the Einstein Extended Medium Sensitivity Survey (EMSS), the EXOSAT High Galactic Latitude Survey, and from the compilations of Giommi et al. (1990ApJ...356..432G) and Veron & Veron (1993ESOSR..13....1V). We find that the shape of the radio to infra-red spectrum of Radio Selected and X-ray Selected BL Lacs is very similar. The difference between these two classes of objects is instead evident in the optical/X-ray part of the spectrum. The classical radio discovered BL Lacs are characterized by an energy spectrum with a sharp cutoff in the IR/optical band while in most of the X-ray discovered objects the turnover is located near the UV/X-ray band or at higher frequencies. For a given X-ray flux this diversity can give rise to radio fluxes different by a factor of 100 or more. We argue that BL Lac objects may be a single population of sources characterized by a wide range of energy cutoffs. In this scenario BL Lacs discovered in radio surveys are representative of the entire population, while objects characterized by an energy break near the X-ray band, which are abundantly detected at X-ray frequencies, are intrinsically a small minority. (5 data files).

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Title:
Radio to X-ray energy distribution of BL Lacertae objects.
Authors:
Giommi, P.; Ansari, S. G.; Micol, A.
Journal:
Astron. Astrophys. Suppl. 109, 267-291 (1995) (A&AS Homepage)
Publication Date:
02/1995
Origin:
A&A via CDS; KNUDSEN
A&A Keywords:
BL LACERTAE OBJECTS: GENERAL, RADIO CONTINUUM: GALAXIES, X-RAY: GALAXIES
Abstract Copyright:
(c) 1995: Astronomy & Astrophysics
Bibliographic Code:
1995A&AS..109..267G

Abstract

We present multifrequency spectra of a large number of radio and X-ray selected BL Lacertae objects constructed using non-simultaneous archival data. The data were obtained using the European Space Information System (ESIS) and are from several radio and optical catalogues, the IRAS Faint Source Catalogue, the Einstein and the EXOSAT databases. The sample includes 121 BL Lacs that have been extracted from the 1Jy and the S4 radio surveys (Stickel et al. 1991; Stickel & Kuehr 1994), the Einstein IPC Slew Survey, the Einstein Extended Medium Sensitivity Survey (EMSS), the EXOSAT High Galactic Latitude Survey, and from the compilations of Giommi et al. (1990), and Veron & Veron (1993). We find that the shape of the radio to infra-red spectrum of Radio Selected and X-ray Selected BL Lacs is very similar. The difference between these two classes of objects is instead evident in the optical/X-ray part of the spectrum. The classical radio discovered BL Lacs are characterized by an energy spectrum with a sharp cutoff in the IR/optical band while in most of the X-ray discovered objects the turnover is located near the UV/X-ray band or at higher frequencies. For a given X-ray flux this diversity can give rise to radio fluxes different by a factor of 100 or more. We argue that BL Lac objects may be a single population of sources characterized by a wide range of energy cutoffs. In this scenario BL Lacs discovered in radio surveys are representative of the entire population, while objects characterized by an energy break near the X-ray band, which are abundantly detected at X-ray frequencies, are intrinsically a small minority.

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Title:
The European Space Information System (ESIS)
Authors:
Giommi, Paolo; Ansari, Salim G.
Journal:
Information & On-Line Data in Astronomy, edited by Daniel Egret and Miguel A. Albrecht. ISBN 0-7923-3659-3, 1995. Astrophysics and Space Science Library, Vol. 203, p.185
Publication Date:
00/1995
Origin:
ADS
Bibliographic Code:
1995ioda.book..185G

Abstract

Not Available

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Title:
The European Space Information System (ESIS)
Authors:
Giommi, P.; Ansari, S. G.; Donzelli, P.; Micol, A.
Journal:
Experimental Astronomy, v. 6, p. 143-162. (ExA Homepage)
Publication Date:
00/1995
Origin:
KLUWER
Bibliographic Code:
1995ExA.....6..143G

Abstract

Not Available

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Title:
The 1985-86 Episodes of AG Draconis
Authors:
Viotti, R.; Giommi, P.; Friedjung, M.; Altamore, A.
Journal:
Cataclysmic Variables, Proceedings of the conference held in Abano Terme, Italy, 20-24 June 1994 Publisher: Dordrecht Kluwer Academic Publisher:s, 1995. Edited by A. Bianchini, M. della Valle, and M. Orio. Astrophysics and Space Science Library, Vol. 205, ISBN 0792336763., p.195
Publication Date:
00/1995
Origin:
ADS
Bibliographic Code:
1995cava.conf..195V

Abstract

Not Available

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Title:
A Method for Visualizing Time Variability in X-Ray Images
Authors:
Giommi, P.; White, N. E.; Angelini, L.
Affiliation:
AA(ESIS, Information Systems Division, ESA/ESRIN, Frascati, Italy), AB(HEASARC, NASA/GSFC, Greenbelt, MD 20771)
Journal:
Astronomical Data Analysis Software and Systems IV, ASP Conference Series, Vol. 77, 1995, R.A. Shaw, H.E. Payne, and J.J.E. Hayes, eds., p. 117.
Publication Date:
00/1995
Origin:
ADASS
Bibliographic Code:
1995adass...4..117G

Abstract

We present a new method for visualizing flux variations in X-ray images. Starting from event list files, images are created where the pixel intensity is proportional to the probability that a strong variation in flux (approximately a factor 2 or more) occurred during the observation. The method is based on the Kolmogorov-Smirnov test and is not sensitive to data interruptions due to temporary loss of telemetry, earth occultations etc. Since only strong variations can be detected this approach is also insensitive to most spurious events induced by satellite pointing instability. This method has been implemented within the XIMAGE package and was used during a systematic analysis of all publicly available ROSAT PSPC images. The results of this analysis were used to construct the WGA catalog of X-ray sources. In this paper we describe the method and give some specific examples. The results presented here make use of the ROSAT PSPC data obtained from the ROSAT public archive accessible via the ESIS or the HEASARC systems.

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Title:
The X-ray spectra of blazars: Analysis of the complete EXOSAT archive
Authors:
Sambruna, Rita M.; Barr, Paul; Giommi, Paolo; Maraschi, Laura; Tagliaferri, Gianpiero; Treves, Aldo
Affiliation:
AA(International School for Advanced Studies, Trieste, Italy), AB(International School for Advanced Studies, Trieste, Italy), AC(European Space Information System, Frascati, Italy), AD(European Space Information System, Frascati, Italy), AE(Osservatorio Astronomico di Brera, Milan, Italy), AF(Osservatorio Astronomico di Brera, Milan, Italy)
Journal:
Astrophysical Journal Supplement Series (ISSN 0067-0049), vol. 95, no. 2, p. 371-385 (ApJS Homepage)
Publication Date:
12/1994
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
ASTRONOMICAL CATALOGS, BL LACERTAE OBJECTS, QUASARS, STELLAR MODELS, X RAY ASTRONOMY, X RAY SPECTRA, ASTRONOMICAL SPECTROSCOPY, EXOSAT SATELLITE, MATHEMATICAL MODELS, OXYGEN, SPACEBORNE ASTRONOMY
Bibliographic Code:
1994ApJS...95..371S

Abstract

We analyzed the 0.1-10 keV spectra of 26 blazars (21 BL Lac objects and 5 highly polarized quasars), on the basis of 93 exposures taken from the EXOSAT archives. Fits were performed first with a single power-law model. Indications are found that better fits can be obtained with models where the slope steepens at higher energies. We therefore considered a broken power law and found that in a large fraction of the spectra the fit is significantly improved. Fits with a power law + oxygen edge at 0.6 keV are also explored.

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Title:
Probing BL Lac and Cluster Evolution via a Wide-angle, Deep X-ray Selected Sample
Authors:
Perlman, E.; Jones, L.; White, N.; Angelini, L.; Giommi, P.; McHardy, I.; Wegner, G.
Affiliation:
AA(GSFC), AB(GSFC), AC(GSFC), AD(GSFC), AE(ESA/ESRIN), AF(Southampton), AG(Dartmouth)
Journal:
American Astronomical Society, 185th AAS Meeting, #110.10; Bulletin of the American Astronomical Society, Vol. 26, p.1507
Publication Date:
12/1994
Origin:
AAS
Abstract Copyright:
(c) 1994: American Astronomical Society
Bibliographic Code:
1994AAS...18511010P

Abstract

The WARPS survey (Wide-Angle ROSAT Pointed Survey) has been constructed from the archive of all public ROSAT PSPC observations, and is a subset of the WGACAT catalog. WARPS will include a complete sample of >= 100 BL Lacs at F_x >= 10(-13) erg s(-1) cm(-2) . A second selection technique will identify ~ 100 clusters at 0.15<z<1, and ~ 50 bright NELGs (Narrow Emission-Line Galaxies). We will detail the search methods used in producing these samples, as well as their benefits. Only 171 BL Lacs are known and the largest complete samples are also small, with 20-50 objects each. Current data shows a discrepancy between XBL (X-ray selected BL Lac) and RBL (Radio-selected BL Lac) evolution, with <V/V_{max}> = 0.304 +/- 0.062 for XBLs but <V/V_{max}> = 0.60 +/- 0.05 for RBLs. Models of the X-ray luminosity function (XLF) are also poorly constrained. WARPS will allow us to compute an accurate XLF, decreasing the error bars above by over a factor of two. We will also test for low-luminosity BL Lacs, whose non-thermal nuclear sources are dim compared to the host galaxy. Browne and Marcha (1993) claim the EMSS missed most of these objects and is incomplete. If their predictions are correct, 20-40% of the BL Lacs we find will fall in this category, enabling us to probe the evolution and internal workings of BL Lacs at lower luminosities than ever before. By removing likely QSOs before optical spectroscopy, WARPS requires only modest amounts of telescope time. It will extend measurement of the cluster XLF both to higher redshifts (z>0.5) and lower luminosities (L_{X}<1x10(44) erg s(-1) ) than previous measurements, confirming or rejecting the 3sigma detection of negative evolution found in the EMSS, and constraining Cold Dark Matter cosmologies. Faint NELGs are a recently discovered major contributor to the X-ray background. They are a mixture of Sy2s, starbursts and galaxies of unknown type. Detailed classification and evolution of their XLF will be determined for the first time.

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Title:
The WGA Catalog of ROSAT Sources: First Results on Time Variability
Authors:
Giommi, P.; White, N. E.; Angelini, L.
Affiliation:
AA(ESIS/ESA), AB(LHEA/GSFC), AC(LHEA/GSFC)
Journal:
American Astronomical Society, 185th AAS Meeting, #41.12; Bulletin of the American Astronomical Society, Vol. 26, p.1372
Publication Date:
12/1994
Origin:
AAS
Abstract Copyright:
(c) 1994: American Astronomical Society
Bibliographic Code:
1994AAS...185.4112G

Abstract

The ROSAT WGA catalog includes more than 40,000 soft X-ray sources detected in archival PSPC images. Each source was tested for time variability using a Kolmogorov Smirnov method which allowed us to find several hundred rapidly variable objects. Among the already identified variable sources the majority are flare stars, but X-ray transients and a number of AGN have also been found. About 1800 entries in the WGA catalog also appear in the list of Einstein IPC sources. These have been tested for long term ( ~ gt 10 years) variability. Most types of objects exhibit large amplitude variations on this time scale with late type stars showing the widest range of variability. Within the class of AGN preliminary results indicate that the amplitude of variability decreases with redshift and that there is no obvious correlation with luminosity.

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Title:
The WGA Catalog of ROSAT Point Sources
Authors:
White, N. E.; Giommi, P.; Angelini, L.
Affiliation:
AA(LHEA/GSFC), AB(ESIS/ESA), AC(LHEA/GSFC)
Journal:
American Astronomical Society, 185th AAS Meeting, #41.11; Bulletin of the American Astronomical Society, Vol. 26, p.1372
Publication Date:
12/1994
Origin:
AAS
Abstract Copyright:
(c) 1994: American Astronomical Society
Bibliographic Code:
1994AAS...185.4111W

Abstract

We have taken all the data available from the ROSAT public archive as of September 1994 and used a sliding box detection technique to generate a catalog of point sources. This catalog currently contains in excess of 40,000 entries and is by far the largest public list of X-ray sources. It will be released through the HEASARC and ESIS online services in November 1994. A cross-correlation against all the major catalogs has allowed a preliminary identification of known optical, radio, X-ray and IR objects, but these represent a small fraction of the catalog. The sky coverage and various catalog overview parameters will be presented. A hardness and softness ratio is also used to identify unusually soft or hard sources. The arrival time distribution of the photons collected for each detected source is compared with the corresponding distribution of the entire image using a Kolmogorov-Smirnov (KS) test. The result of the KS test is a chi (2) value which is then used to test for highly variable sources. A number of flaring X-ray sources have been discovered, including a new recurrent super-soft X-ray transient in M31.

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Title:
WGACAT.
Authors:
White, N. E.; Giommi, P.; Angelini, L.
Journal:
IAU Circ., 6100, 1 (1994) (IAUC Homepage)
Publication Date:
11/1994
Origin:
SIMBAD
Bibliographic Code:
1994IAUC.6100Q...1W

Abstract

Not Available

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Title:
WGACAT
Authors:
White, N. E.; Giommi, P.; Angelini, L.
Journal:
IAU Circ., 6100, 1 (1994). Edited by Marsden, B. G. (IAUC Homepage)
Publication Date:
11/1994
Origin:
CBAT
Bibliographic Code:
1994IAUC.6100....1W

Abstract

IAUC 6100 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
The X-ray spectra of blazars observed with EXOSAT
Authors:
Sambruna, Rita M.; Barr, Paul; Giommi, Paolo; Maraschi, Laura; Tagliaferri, Gianpiero; Treves, Aldo
Affiliation:
AA(SISSA/ISAS, Trieste, Italy), AB(SISSA/ISAS, Trieste, Italy), AC(ESA/ESRIN, Frascati, Italy), AD(ESA/ESRIN, Frascati, Italy), AE(Osservatorio Astronomico di Brera, Milano, Italy), AF(Osservatorio Astronomico di Brera, Milano, Italy)
Journal:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 434, no. 2, p. 468-478 (ApJ Homepage)
Publication Date:
10/1994
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ASTRONOMICAL MODELS, BL LACERTAE OBJECTS, LUMINOSITY, POWER SERIES, QUASARS, X RAY ASTRONOMY, X RAY SPECTRA, EXOSAT SATELLITE, HEAO 1, HEAO 2, OPTICAL POLARIZATION, RADIO EMISSION
Bibliographic Code:
1994ApJ...434..468S

Abstract

A sytematic analysis of the X-ray spectra (0.1-10 keV) of all blazars observed with EXOSAT is presented. The objects include 16 X-ray-selected BL Lac objects (XBLs), five radio-selected BL Lac objects (RBLs), and five highly polarized quasars (HPQs). Comparing the results of single-power-law fits for the different classes, we find that XBLs have steeper X-ray spectra than HPQs (average photon indices mean value of Gamma approximately = (2.20+0.17-0.15) and (1.62+0.11)-0.24, repectively). The X-ray luminosities of XBLs and RBLs are similar, while HPQs tend to be somewhat more luminous. For the three groups, a correlation between the average medium-energy luminosity and the average spectral index is found, in the sense that sources of higher luminosity have flatter spectra. For repeatedly observed objects (XBLs), the spectra harden systematically with increasing intensity. For seven (out of 16) XBLs, corresponding to the brightest objects in the sample, the X-ray spectrum is significantly better described by a convex, broken-power-law model than by a single power law. The results are discussed in the framework of current models for blazars.

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Title:
RX J0045.4+4154
Authors:
White, N. E.; Giommi, P.; Angelini, L.; Fantasia, S.
Journal:
IAU Circ., 6064, 1 (1994). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
08/1994
Origin:
CBAT
Objects:
RX J0045.4+4154
Bibliographic Code:
1994IAUC.6064....1W

Abstract

IAUC 6064 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
Bl-Lacertae Reunification
Authors:
Giommi, P.; Padovani, P.
Journal:
R.A.S. MONTHLY NOTICES V.268, NO. 2/MAY15, P. L51, 1994 (MNRAS Homepage)
Publication Date:
05/1994
Origin:
KNUDSEN; NED
Bibliographic Code:
1994MNRAS.268L..51G

Abstract

X-ray-selected BL Lacs (XBLs) are generally thought to outnumber the more extreme radio-selected objects (RBLs), on the grounds that their properties could be understood if the X-ray jet were broader than the radio one. Here we present an alternative explanation: RBLs and XBLs may well be two aspects of the same population, whose main difference is the frequency of the high-energy cut-off in their energy distribution, with XBLs constituting the small subclass with cut-offs at X-ray (or higher) energies. Under this assumption, we are able to reproduce the X-ray number counts of XBLs starting from the radio counts of RBLs. We also calculate the distribution of radio fluxes of BL Lacs in current and future (deeper) X-ray surveys (e.g ROSAT), wherein we predict that a strong selection effect arising from radio constraints will lead to the preferential discovery of objects of the RBL kind. our hypothesis implies that there is a single family of BL Lacs and that, within this family, XBL-like objects are a small minority, contrary to the common belief that they represent the most numerous class.

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Title:
15-30 arcsec resolution replica x-ray optics for AXAF-S
Authors:
Stella, Luigi; Chincarini, G.; Citterio, Oberto; Conconi, Paolo; Maccacaro, T.; Tagliaferri, G.; Trinchieri, G.; Wolter, A.; Bignami, Giovanni F.; Bocchino, F.; Maggio, A.; Micela, G.; Sciortino, Salvatore; Serio, Salvatore; Collura, Alfonso; Giommi, P.; Maraschi, L.; Pallavicini, R.; Pellegrini, S.; Peres, G.
Affiliation:
AA(Osservatorio Astronomico di Brera) AI(Univ. di Cassino and CNR-IFCTR) AJ(Osservatorio Astronomico di Palermo) AO(CNR-IAIF) AP(ESA-ESRIN) AQ(Univ. di Genova and Univ. di Milano) AR(Osservatorio Astronomico di Arcetri) AS(Osservatorio Astronomico di Bologna) AT(Osservatorio Astrofisico di Catania)
Journal:
Proc. SPIE Vol. 2011, p. 149-160, Multilayer and Grazing Incidence X-Ray/EUV Optics II, Richard B. Hoover; Arthur B. Walker; Eds. (SPIE Homepage)
Publication Date:
02/1994
Origin:
SPIE
Abstract Copyright:
(c) 1994 SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Bibliographic Code:
1994SPIE.2011..149S

Abstract

This document describes a proposal for a replica X-ray optics to be developed in Italy for NASA's X-ray spectroscopy mission AXAF-S. The program is based on state of the art technology for the production of replica X-ray optics. On the basis of the experience with the Jet-X mirror shells (to be flown on the Spectrum X-(gamma) satellite), a spatial resolution of 15 - 30 arcsec half power diameter (HPD) can be achieved for the AXAF-S optics. The characteristics of the proposed optical system are described and its performances evaluated by using the current baseline configuration for the array of X-ray calorimeters in the focal plane. The impact of the proposed replica X-ray optics is briefly outlined and a comparison with foil optics (1 - 3 arcmin HPD resolution) is carried out.

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Title:
Optical Properties of Soft X-ray Selected Bright New ROSAT AGN
Authors:
Giommi, P.; Ansari, S. G.; Micol, A.
Journal:
Multi-wavelength continuum emission of AGN: proceedings of the 159th Symposium of the International Astronomical Union; held in Geneva; Switzerland; August 30-September 3; 1993. Edited by T. Courvoisier and A. Blecha. International Astronomical Union. Symposium no. 159; Kluwer Academic Publishers; Dordrecht, p.506
Publication Date:
00/1994
Origin:
ADS
Bibliographic Code:
1994IAUS..159..506G

Abstract

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Title:
The European Space Information System
Authors:
Giommi, P.; Ansari, S. G.
Journal:
Frontiers of Space and Ground-Based Astronomy: The Astrophysics of the 21st century, Dordrecht, Boston: Kluwer Academic Publishers, |c1994, edited by W. Wamsteker, Malcolm. S. Longair, and Y. Kondo. Astrophysics and Space Science Library, Vol. 187, p.725
Publication Date:
00/1994
Origin:
ADS
Bibliographic Code:
1994fsgb.book..725G

Abstract

Not Available

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Title:
The X-Ray Spectra of Blazars: Analysis of the Complete EXOSAT Archive
Authors:
Sambruna, R. M.; Treves, A.; Barr, P.; Giommi, P.; Maraschi, L.; Tagliaferri, G.
Journal:
Frontiers of Space and Ground-Based Astronomy: The Astrophysics of the 21st century, Dordrecht, Boston: Kluwer Academic Publishers, |c1994, edited by W. Wamsteker, Malcolm. S. Longair, and Y. Kondo. Astrophysics and Space Science Library, Vol. 187, p.681
Publication Date:
00/1994
Origin:
ADS
Bibliographic Code:
1994fsgb.book..681S

Abstract

Not Available

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Title:
The ESIS Spectral Package
Authors:
Ansari, S. G.; Giommi, P.; Ulla, A.
Journal:
Astronomical Data Analysis Software and Systems III, A.S.P. Conference Series, Vol. 61, 1994, Dennis R. Crabtree, R.J. Hanisch, and Jeannette Barnes, eds., p. 447.
Publication Date:
00/1994
Origin:
ADASS
Bibliographic Code:
1994adass...3..447A

Abstract

The ESIS Spectral package provides access to a number of multiwavelength data through a graphic user interface, which contains a variety of tools for pre-analysis of spectra. Currently, ESIS provides access to EXOSAT ME and GSPC, Einstein SSS, IUE Low Dispersion, and IRAS Low Resolution spectra, which can be homogeneously accessed for any given object. The package features chemical element identification of spectral lines, automatic redshift correction, de-redenning of UV data, and a radio to X-ray energy distribution of single objects. Other functions will be shortly implemented. The spectral package provides links to native mode analysis packages, such as XSPEC and in the future, other packages, such as MIDAS and IRAF will be made available. A UNIX version of the ESIS spectral package is under current developement. In this paper, we discuss the functionalities of ESIS spectral package tool, the algorithms used for the various functions and give a number of examples to demonstrate its advantages.

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Title:
Homogeneous Access to Data: The ESIS Reference Directory
Authors:
Ansari, S. G.; Giommi, P.; Micol, A.; Natile, P.
Journal:
Astronomical Data Analysis Software and Systems III, A.S.P. Conference Series, Vol. 61, 1994, Dennis R. Crabtree, R.J. Hanisch, and Jeannette Barnes, eds., p. 139.
Publication Date:
00/1994
Origin:
ADASS
Bibliographic Code:
1994adass...3..139A

Abstract

An important component of ESIS that controls the system is the ESIS Reference Directory. This metadatabase contains a variety of information on remotely-accessed images, spectra or light curves. It plays an important role in the homogeneous access of a variety of astronomical catalogues, by the use of a strict naming convention of fields, providing commands which are used in conjunction with the display and manipulation packages of ESIS to remotely access the data. We discuss in this paper the methods used to set up a reference directory as a central repository and mechanisms used to access the metadata to resolve ESIS queries and the methods used to access the data.

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Title:
The European Space Information System (ESIS)
Authors:
Giommi, P.; Ansari, S.
Journal:
Astronomical Data Analysis Software and Systems III, A.S.P. Conference Series, Vol. 61, 1994, Dennis R. Crabtree, R.J. Hanisch, and Jeannette Barnes, eds., p. 22.
Publication Date:
00/1994
Origin:
ADASS
Bibliographic Code:
1994adass...3...22G

Abstract

The European Space Information System (ESIS) is an ESA service that provides uniform access to astronomical data and bibliographical information from several remote archives. ESIS is a new generation data system that gives access to astronomical catalogues and data products such as images, spectra and lightcurves using a powerful and easy-to-use graphic user interface. Extensive facilities to visualize, compare and correlate data from different archives are included. Currently ESIS supports data retrieval from the IUE, EXOSAT, HST, Einstein and SIMBAD databases. Several catalogues and mission logs, including GINGA, and ROSAT are also available. A first version of the ESIS system has been recently released and can be publicly accessed through computer networks. A client-server version of the system is also available and has been installed at a number of astronomical institutes. Demonstrations will be given during the conference.

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Title:
Multiwavelength astronomy using ESIS
Authors:
Giommi, P.; Ansari, S. G.
Affiliation:
AA(ESA/ESRIN, Frascati, Italy), AB(ESA/ESRIN, Frascati, Italy)
Journal:
Advances in Space Research (ISSN 0273-1177), vol. 13, no. 12, p. (12)621-(12)625 (AdSpR Homepage)
Publication Date:
12/1993
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
AEROSPACE SCIENCES, DATA BASES, INFORMATION SYSTEMS, INFRARED ASTRONOMY, LIGHT (VISIBLE RADIATION), RADIO ASTRONOMY, ULTRAVIOLET ASTRONOMY, X RAY ASTRONOMY, ACTIVE GALACTIC NUCLEI, ASTRONOMICAL CATALOGS, EUROPEAN SPACE AGENCY, EXOSAT SATELLITE, HEAO 2, IMAGERY, INFRARED ASTRONOMY SATELLITE, IUE, SEYFERT GALAXIES, SPECTRAL ENERGY DISTRIBUTION, SPECTROGRAMS
Bibliographic Code:
1993AdSpR..13..621G

Abstract

We present results on multi-frequency astronomy obtained using the European Space Information System (ESIS). ESIS is an ESA service designed to access, manipulate and combine archival data from a number of remote archives in the fields of Astronomy and Space Physics. The examples presented here include plots of radio-to-X-ray energy distribution of Active Galactic Nuclei, spectrograms of IUE/UV data, direct comparison of images from different experiments and overlay of catalogue sources on image data. The ESIS project is currently reaching the end of its pilot phase. Its services will be available to the general astronomical community in 1993.

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Title:
X-ray luminosity and spectral variability of hard X-ray-selected active galactic nuclei
Authors:
Grandi, P.; Tagliaferri, G.; Giommi, P.; Barr, P.; Palumbo, G. G. C.
Affiliation:
AA(Padova, Universita, Padua; CNR, Istituto di Studio e Tecnologie sulle Radiazioni Extraterrestri, Bologna, Italy), AB(EXOSAT Observatory; ISO Observatory, Noordwijk, Netherlands), AC(EXOSAT Observatory, Noordwijk, Netherlands; ESA, Frascati, Italy), AD(EXOSAT Observatory; ISO Observatory, Noordwijk, Netherlands), AE(CNR, Istituto di Studio e Tecnologie sulle Radiazioni Extraterrestri; Bologna, Universita, Italy)
Journal:
Astrophysical Journal Supplement Series (ISSN 0067-0049), vol. 82, no. 1, Sept. 1992, p. 93-116. Research supported by ASI and MURST. (ApJS Homepage)
Publication Date:
09/1992
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ACTIVE GALACTIC NUCLEI, ASTRONOMICAL SPECTROSCOPY, LIGHT CURVE, LUMINOSITY, QUASARS, X RAY SOURCES, EMISSION SPECTRA, EXOSAT SATELLITE, VARIABILITY
Bibliographic Code:
1992ApJS...82...93G

Abstract

Luminosity and spectral variability are analyzed in a sample of AGNs from Exosat data based on the soft (LE: 0.05-2 keV) and hard (ME: 1-8 keV) light curves. Specific attention is given to flux variability noted in the objects that are observed at least twice, and time variations and fast variability are also reported. The 14 sources that show simultaneous long time variations in both light-curve ranges are also investigated in terms of spectral variability. Flux variability is shown to be very common in AGNs, and a subsample of the AGNs demonstrated changes in spectral shape with flux. Variations in the ratio of the hard/soft light curves are found to be present in 63 percent of the objects investigated. The study of X-ray luminosity and spectral variability in hard-X-ray-selected AGNs shows that no unique spectral behavior can be associated with the objects. Source spectra can be dominated by either a soft independent component or by a variable absorber when ME/LE color steepens.

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Title:
Radio to X-ray Energy Distribution of samples of AGN
Authors:
Giommi, P.; Ansari, S.
Affiliation:
AA(ESA/ESRIN, Frascati, Italy), AB(ESA/ESRIN, Frascati, Italy)
Journal:
American Astronomical Society, 181st AAS Meeting, #35.01; Bulletin of the American Astronomical Society, Vol. 24, p.1172
Publication Date:
09/1992
Origin:
AAS
Abstract Copyright:
(c) 1992: American Astronomical Society
Bibliographic Code:
1992AAS...181.3501G

Abstract

We present a compilation of energy spectra of a number of AGN constructed using archival data obtained and processed with the European Space Information System (ESIS). The set of objects presented includes well known emission line AGN and BL Lacertae Objects and well defined samples such as the Einstein Extended Medium Sensitivity Survey, the IPC Slew Survey and the EXOSAT High Galactic Latitude Survey. Data are from several radio, infrared and optical catalogs, the IRAS, IUE, Einstein and EXOSAT databases.

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Title:
Review of Italsat thermal performances throughout the first eighteen months of operational life
Authors:
Liverani, Stefano; Giommi, Marco; Sacchi, Enrico
Affiliation:
AA(Alenia Spazio S.p.A., Rome, Italy), AB(Alenia Spazio S.p.A., Rome, Italy), AC(Alenia Spazio S.p.A., Rome, Italy)
Journal:
SAE, International Conference on Environmental Systems, 22nd, Seattle, WA, July 13-16, 1992, 10 p.
Publication Date:
07/1992
Category:
Spacecraft Design, Testing and Performance
Origin:
STI
NASA/STI Keywords:
COMMUNICATION SATELLITES, FLIGHT CHARACTERISTICS, PERFORMANCE, SERVICE LIFE, THERMAL ANALYSIS, ARIANE LAUNCH VEHICLE, FRENCH GUIANA, GENERAL OVERVIEWS, ITALIAN SPACE PROGRAM
Bibliographic Code:
1992saei.confX....L

Abstract

The Italsat F1 thermal performances throughout the first 18 months of operation are reviewed with particular attention given to general spacecraft temperature conditions and special equipment thermal behavior. It is concluded that the Italsat thermal control subsystem-related performances are quite satisfactory. The correlation achieved by comparison between predicted and observed temperatures confirms the validity of the spacecraft thermal mathematical model.

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Title:
Extensive X-ray monitoring of the broad-line galaxy 3C 382
Authors:
Barr, P.; Giommi, P.
Affiliation:
AA(EXOSAT Observatory, Noordwijk, Netherlands), AB(EXOSAT Observatory, Noordwijk, Netherlands)
Journal:
Royal Astronomical Society, Monthly Notices (ISSN 0035-8711), vol. 255, April 1, 1992, p. 495-501. (MNRAS Homepage)
Publication Date:
04/1992
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
EXOSAT SATELLITE, LIGHT CURVE, RADIO GALAXIES, X RAY ASTRONOMY, CROSS CORRELATION, RED SHIFT
Bibliographic Code:
1992MNRAS.255..495B

Abstract

The results of an intensive monitoring campaign of the X-ray light curve of the broad-line radio galaxy 3C 382, performed using the Exosat observatory over a five-month period in summer 1985, are presented. Significant variations on a time-scale of several days are found in both the hard and soft X-ray bands, probably superimposed on a systematic long-term (months) trend. However, no evidence was found for such variability on shorter time-scales. A variable soft excess is seen with the Low Energy telescope. The soft excess seems coupled to the hard X-ray continuum on long time-scales (months) but not on a short time-scales (weeks or less). It is suggested that long-term variations could be associated with a common power source for both soft and hard X-ray emission, perhaps associated with details of the accretion process, while rapid variability may indicate different emission mechanisms in the two energy bands.

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Title:
X ray luminosity and spectral variability of a complete sample of AGN's
Authors:
Grandi, P.; Palumbo, G. G. C.; Tagliaferri, G.; Giommi, P.; Barr, P.
Affiliation:
AA(Bologna Univ., Italy), AB(Bologna Univ., Italy), AC(European Space Research Lab., Noordwijk, Netherlands), AD(European Space Agency. ESRIN, Rome, Italy), AE(European Space Agency. European Space Research and Technology Center, ESTEC, Noordwijk, Netherlands)
Journal:
In MPI fuer Extraterrestrische Physik, X Ray Emission from Active Galactic Nuclei and the Cosmic X Ray Background p 17-21 (SEE N93-17094 05-90)
Publication Date:
03/1992
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ACTIVE GALACTIC NUCLEI, EMISSION SPECTRA, LINE SPECTRA, LUMINOSITY, VARIABILITY, X RAY SPECTRA, BL LACERTAE OBJECTS, DATA REDUCTION, EXOSAT SATELLITE, LIGHT CURVE, X RAY ASTRONOMY, X RAY SOURCES
Bibliographic Code:
1992xrea.conf...17G

Abstract

One hundred and sixty one Exosat observations of 30 emission line Active Galactic Nuclei (AGN's) in the Piccinotti sample were studied for variability. For each source long (from days to months) and short (from minutes to hours) term luminosity variations were searched for using soft (LE: 0.05 to 2 keV) and long (ME: 1 to 8 keV) light curves. Spectral variability was also investigated for all the 14 objects that showed long time variations in both the energy bands.

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Title:
EXOSAT X-ray spectra of quasars
Authors:
Comastri, Andrea; Setti, Giancarlo; Zamorani, Giovanni; Elvis, Martin; Wilkes, Belinda J.; McDowell, Jonathan C.; Giommi, Paolo
Affiliation:
AA(Bologna, Universita; CNR, Istituto di Radioastronomia, Italy), AB(CNR, Istituto di Radioastronomia; Bologna, Universita, Italy; European Southern Observatory, Garching, Federal Republic of Germany), AC(Osservatorio Astronomico; CNR, Istituto di Radioastronomia, Bologna, Italy), AD(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AE(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AF(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AG(EXOSAT Observatory, Noordwijk, Netherlands)
Journal:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 384, Jan. 1, 1992, p. 62-71. Research supported by Harvard-Smithsonian Center for Astrophysics. (ApJ Homepage)
Publication Date:
01/1992
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
EXOSAT SATELLITE, QUASARS, X RAY SPECTRA, GALACTIC NUCLEI, SEYFERT GALAXIES
Bibliographic Code:
1992ApJ...384...62C

Abstract

Measurements of the X-ray spectra in the 0.1-10-keV energy range for 17 AGN (mostly PG quasars) using the Exosat Low and Medium Energy arrays are presented. For each object, the best-fit spectral parameters in the medium-energy range (about 2-10 keV), i.e., the power-law slope, the normalization, and the absorbing column density, are determined. In this energy range, all the spectra are well described by a single power law model, with a wide distribution of energy spectral indices in the range 0.4-1.3. The average spectral index is 0.89 +/-0.06, but most of the objects are distributed around 1.0. Inclusion of lower energy data (about 0.1-2.0 keV) shows the presence of significant soft excess in six out of 17 cases. This soft excess emission can be modeled by either a steep power law with the average spectral index ranging from 2.7 to 4.2 or the high-energy tail of a blackbody with temperatures in the range 40-80 eV.

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Title:
Optical Properties of Cool Stars Discovered by EXOSAT
Authors:
Tagliaferri, G.; Cutispoto, G.; Giommi, P.; Pallavicini, R.; Pasquini, L.; Rodonó, M.
Journal:
Surface Inhomogeneities on Late-Type Stars, Proceedings of a colloquium held at Armagh Observatory, Northern Ireland, 24-27 July, 1990. Edited by Patrick B. Byrne and Dermott J. Mullan. Lecture Notes in Physics, Vol. 397. Published by Springer-Verlag, Heidelberg, Germany, 1992., p.340
Publication Date:
00/1992
Origin:
ADS
Bibliographic Code:
1992sils.conf..340T

Abstract

Not Available

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Title:
Optical Spectroscopy of Cool Stars Detected by EXOSAT
Authors:
Tagliaferri, G.; Cutispoto, G.; Giommi, P.; Pallavicini, R.; Pasquini, L.; Rodono, M.
Journal:
Cool stars, stellar systems, and the sun, Proceedings of the 7th Cambridge Workshop, ASP Conference Series (ASP: San Francisco), vol. 26, p. 122.
Publication Date:
00/1992
Origin:
ADS
Bibliographic Code:
1992csss....7..122T

Abstract

Not Available

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Title:
XIMAGE a Multi-Mission X-ray Image Analysis Package
Authors:
Giommi, P.; Angelini, L.; Jacobs, P.; Tagliaferri, G.
Affiliation:
AA( ESIS, Information Systems Division, ESA/ESRIN, Frascati, Italy), AA( HEASARC, GSFC, Greenbelt, MD, USA), AA( Astrophysics Division, ESA/ESTEC, Noordwijk, The Netherlands)
Journal:
Astronomical Data Analysis Software and Systems I, A.S.P. Conference Series, Vol. 25, 1992, Diana M. Worrall, Chris Biemesderfer, and Jeannette Barnes, eds., p. 100.
Publication Date:
00/1992
Origin:
ADASS
Bibliographic Code:
1992adass...1..100G

Abstract

XIMAGE is a portable X-ray image analysis and simulation package that supports the analysis of EXOSAT, Einstein and ROSAT data. Other X-ray imaging detectors can be supported provided that the proper calibration files are available. The graphic capabilities of XIMAGE are based on PGPLOT which supports most graphic terminals, and on SAOIMAGE which runs on X-Window. XIMAGE supports several data analysis tasks including a slide-cell detect and the simulation of data from present and future detectors. XIMAGE can be run as a standalone program or within the EXOSAT Database System (EXOSAT Observatory team 1991a,b) or from the ESIS Correlation Environment Prototype (Giommi et al. 1992). The XIMAGE code is written in FORTRAN77, runs on VAX/VMS and SUN/UNIX machines and is available on request at no cost.

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Title:
The ESIS Correlation Environment Prototype
Authors:
Giommi, P.; Ansari, S. G.; Ciarlo, A.; Donzelli, P.; Stokke, H.; Torrente, P.; Walker, S.; Zampognaro, V.
Affiliation:
AA(ESIS, Information Systems Division, ESA/ESRIN, Frascati, Italy), AG(Cap Gemini Sesa Italia, Rome, Italy)
Journal:
Astronomical Data Analysis Software and Systems I, A.S.P. Conference Series, Vol. 25, 1992, Diana M. Worrall, Chris Biemesderfer, and Jeannette Barnes, eds., p. 59.
Publication Date:
00/1992
Origin:
ADASS
Bibliographic Code:
1992adass...1...59G

Abstract

This paper gives a brief description of the Correlation Environment Prototype currently under development at ESRIN (Frascati, Italy) as part of the European Space Information System (ESIS) project. The prototype consists of a C program that acts as graphical user-interface, as tasks scheduler and as data-handler within the general ESIS system. This program will provide a uniform view to a number of applications that allow the user to retrieve, inspect and compare Astronomy and Space-Physics data. The prototype architecture is object oriented and open so that new packages can easily be included as they become available. The prototype will run on VAX-VMS and on UNIX systems.

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Title:
Italsat thermal control: The in-orbit performances
Authors:
Giommi, Marco; Liverani, Stefano; Sacchi, Enrico
Affiliation:
Alenia Spazio S.p.A., Rome (Italy).
Journal:
In ESA, 4th European Symposium on Space Environmental Control Systems, Volume 2 p 931-937 (SEE N92-26950 17-54)
Publication Date:
12/1991
Category:
Spacecraft Design, Testing and Performance
Origin:
STI
NASA/STI Keywords:
COMMUNICATION SATELLITES, MATHEMATICAL MODELS, PERFORMANCE TESTS, SATELLITE TEMPERATURE, SPACECRAFT DESIGN, TEMPERATURE CONTROL, THERMAL SIMULATION, POSTMISSION ANALYSIS (SPACECRAFT), STRUCTURAL ANALYSIS, THERMAL ANALYSIS, THERMAL VACUUM TESTS
Bibliographic Code:
1991secs....2..931G

Abstract

Italsat F1 is a three axes stabilized communication satellite. The Italsat system consists of a global beam and a multibeam package (20/30 GHz) for domestic communication services and an experimental propagation package at 40/50 GHz with European coverage. The spacecraft thermal control design was experimentally qualified by means of a solar simulation test performed on a dedicated structural and thermal model. Correlation analysis with test temperatures was performed in order to verify the thermal mathematical models. The flight unit was submitted to a thermal vacuum test in order to prove the system performances. Dedicated thermal balance phases allowed verification of the final spacecraft thermal design. Italsat F was successfully launched by Ariane 4 on Jan. 15 1991. It is presently on station on the nominal operating configuration. Flight temperatures to date show excellent performance of the spacecraft thermal control. Spacecraft thermal design and test verification methods are provided. In orbit thermal performance as well as analysis correlation with test and flight temperatures are presented and discussed.

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Title:
Persistence and change in the soft X-ray spectrum of the quasar PG 1211 + 143
Authors:
Elvis, Martin; Wilkes, Belinda J.; Giommi, P.; McDowell, Jonathan
Affiliation:
AA(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AB(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AC(EXOSAT Observatory, Noordwijk, Netherlands), AD(NASA, Marshall Space Flight Center, Huntsville, AL; Harvard-Smithsonian Center for Astrophysics, Cambridge, MA)
Journal:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 378, Sept. 10, 1991, p. 537-542. (ApJ Homepage)
Publication Date:
09/1991
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
QUASARS, STELLAR SPECTRA, X RAY SOURCES, X RAY SPECTRA, EXOSAT SATELLITE, OPTICAL THICKNESS, SATELLITE OBSERVATION
Bibliographic Code:
1991ApJ...378..537E

Abstract

The present study examines two Einstein and three Exosat observations of PG 1211 + 143 over a 6-yr baseline which show that strong steep-spectrum low-energy X-ray emission is a persistent feature of this quasar. Exosat observations of PG 1211 + 143 detected an increase of a factor of 2.3 in its steep soft X-ray flux during 18 days. It is concluded that the bulk of the soft X-ray emission of PG 1211 + 143 comes from a region less than 5 x 10 to the 16th cm across. In another interval of 193 days, the soft X-rays decreased by a factor of 3.7. In the same interval the hard X-rays decreased by a factor of 1.6 + or - 0.05, which suggests a connection between the two energy regimes and argues against variable absorption causing the soft X-ray variations. It is contended that in order to decrease in luminosity so rapidly, a thermal source in PG 1211 + 143 would have to be optically thick to both electron scattering and free-bound absorption.

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Title:
The EXOSAT high Galactic latitude survey
Authors:
Giommi, P.; Tagliaferri, G.; Beuermann, K.; Branduardi-Raymont, G.; Brissenden, R.; Graser, U.; Mason, K. O.; Mittaz, J. D. P.; Murdin, P.; Pooley, G.; Thomas, H.-C.; Tuohy, I.
Affiliation:
AA(EXOSAT Observatory, Noordwijk, Netherlands), AB(EXOSAT Observatory, Noordwijk, Netherlands), AC(Berlin, Technische Universitaet; Max-Planck-Institut fuer Extraterrestrische Physik, Garching, Federal Republic of Germany), AD(London, University College, Dorking, England), AE(London, University College, Dorking, England), AF(London, University College, Dorking, England), AG(Australian National University, Canberra, Australia), AH(Max-Planck-Institut fuer Astronomie, Heidelberg, Federal Republic of Germany), AI(Royal Greenwich Observatory, Cambridge, England), AJ(Mullard Radio Astronomy Observatory, Cambridge, England)
Journal:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 378, Sept. 1, 1991, p. 77-92. Research supported by Royal Society and SERC. (ApJ Homepage)
Publication Date:
09/1991
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
EXOSAT SATELLITE, SKY SURVEYS (ASTRONOMY), X RAY ASTRONOMY, ABSORPTION SPECTRA, ACTIVE GALACTIC NUCLEI, BL LACERTAE OBJECTS, MILKY WAY GALAXY, WHITE DWARF STARS, X RAY SOURCES
Bibliographic Code:
1991ApJ...378...77G

Abstract

This study presents a survey of serendipitous sources performed in the very soft X-ray band (0.05-2.0 keV) using the Exosat imaging telescopes. It covers 783 sq deg of high Galactic latitude sky and includes 210 serendipitous sources which define a complete (flux-limited) sample. Two hundred of the 210 detected sources are identified via extensive optical and radio observations together with cross-correlations with catalogs of known objects. The log N-log S relation was found to be consistent with that of the Einstein extended Medium-Sensitivity Survey (EMSS) and with the 'Euclidean' value of 1.5. The normalization of the relation is a strong function of the assumed spectral slope of AGN. It is inferred from the consistency with the EMSS results that the average (energy) slope of extragalactic sources in the soft X-ray band is very steep (approximately 1.5). An analysis of the association between AGN detection and Galactic N(H) also shows that the average slope is steep and inconsistent with the canonical value of 0.7.

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Title:
Photometric and spectroscopic studies of cool stars discovered in EXOSAT X-ray images. I - Time variability and spectral classification of eight southern stars
Authors:
Cutispoto, G.; Tagliaferri, G.; Giommi, P.; Gouiffes, C.; Pallavicini, R.; Pasquini, L.; Rodono, M.
Affiliation:
AA(Catania, Osservatorio Astrofisico, Italy), AB(EXOSAT Observatory, Noordwijk, Netherlands), AC(EXOSAT Observatory, Noordwijk, Netherlands), AD(European Southern Observatory, Santiago, Chile), AE(Arcetri, Osservatorio Astrofisico, Florence, Italy)
Journal:
Astronomy and Astrophysics Supplement Series (ISSN 0365-0138), vol. 87, no. 2, Feb. 1991, p. 233-245. Research supported by Ministero dell'Universita e della Ricerca Scientifica e Tecnologica, CNR, and ASI. (A&AS Homepage)
Publication Date:
02/1991
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
COOL STARS, STELLAR SPECTRA, STELLAR SPECTROPHOTOMETRY, VARIABLE STARS, X RAY ASTRONOMY, EMISSION SPECTRA, EXOSAT SATELLITE, SOUTHERN SKY, STELLAR LUMINOSITY, STELLAR MAGNITUDE
Bibliographic Code:
1991A&AS...87..233C

Abstract

As part of a larger program to study the optical properties of serendipitous Exosat sources, optical photometry and low-resolution spectroscopy are presented for eight southern stars which have been identified as optical counterparts of Exosat sources. X-ray flux variability has been detected for three of them. In all three cases the optical counterparts show RS CVn-type variability. Of the remaining five stars, two are found to be variable in the optical. The high X-ray luminosities inferred from the derived spectroscopic parallaxes indicates that these variable sources are all very active systems, possibly RS CVn binaries. The three nonvariable sources are more likely normal main-sequences stars, two of them with a rather high level of coronal emission.

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Title:
Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. I - an 8 month campaign of monitoring NGC 5548 with IUE
Authors:
Clavel, J.; Reichert, G. A.; Alloin, D.; Crenshaw, D. M.; Kriss, G.; Krolik, J. H.; Malkan, M. A.; Netzer, H.; Peterson, B. M.; Wamsteker, W.; Altamore, A.; Baribaud, T.; Barr, P.; Beck, S.; Binette, L.; Bromage, G. E.; Brosch, N.; Diaz, A. I.; Filippenko, A. V.; Fricke, K.; Gaskell, C. M.; Giommi, P.; Glass, I. S.; Gondhalekar, P.; Hackney, R. L.; Halpern, J. P.; Hutter, D. J.; Joersaeter, S.; Kinney, A. L.; Kollatschny, W.; Koratkar, A.; Korista, K. T.; Laor, A.; Lasota, J.-P.; Leibowitz, E.; Maoz, D.; Martin, P. G.; Mazeh, T.; Meurs, E. J. A.; Nair, A. D.; O'Brien, P.; Pelat, D.; Perez, E.; Perola, G. C.; Ptak, R. L.; Rodriguez-Pascual, P.; Rosenblatt, E. I.; Sadun, A. C.; Santos-Lleo, M.; Shaw, R. A.; Smith, P. S.; Stirpe, G. M.; Stoner, R.; Sun, W. H.; Ulrich, M.-H.; van Groningen, E.; Zheng, W.
Affiliation:
AA(IUE Observatory, Madrid, Spain), AB(IUE Observatory, Madrid, Spain), AC(NASA, Goddard Space Flight Center; Computer Sciences Corp., Greenbelt, MD), AD(NASA, Goddard Space Flight Center; Computer Sciences Corp., Greenbelt, MD), AE(Paris, Observatoire, Meudon, France)
Journal:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 366, Jan. 1, 1991, p. 64-81. (ApJ Homepage)
Publication Date:
01/1991
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ACTIVE GALACTIC NUCLEI, ASTRONOMICAL SPECTROSCOPY, GALACTIC STRUCTURE, IUE, SEYFERT GALAXIES, EMISSION SPECTRA, TIME SERIES ANALYSIS, ULTRAVIOLET SPECTRA, VARIABILITY
Bibliographic Code:
1991ApJ...366...64C

Abstract

Emission-line and UV continuum observations of the type I Seyfert galaxy NGC 5548 were carried out for a period of 8 months with the IUE satellite. It was found that both the continuum shape and the line ratios of NGC 5548, while being not unusual for type I Seyfert galaxies, are strongly variable. The UV continuum flux and broad emission line fluxed went through three large maxima and three deep minima; the ratio of miximum to minimum flux was about 4.5 for the continuum at 1350 A. The N V and the He II emission lines exhibited maximum-to-minimum flux ratios as high as those of the continuum; other ionization lines (Ly-alpha, C IV, and C III) exhibited smaller amplitude fluctuations, with the smallest being recorded for the Mg II line (about 1.3). It was found that, except for Mg II, the emission-line variations correlated extremely well with those of the 1350-A continuum.

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Title:
The EXOSAT Database System
Authors:
White, N. E.; Giommi, P.
Journal:
Databases and On-line Data in Astronomy, edited by Miguel A. Albrecht and Daniel Egret ISBN 0-7923-1247-3; 1991 Astrophysics & Space Science Library vol. 171, p. 11
Publication Date:
00/1991
Origin:
ADS
Bibliographic Code:
1991doda.conf...11W

Abstract

Not Available

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Title:
EXOSAT observations of three DA white dwarfs
Authors:
Koester, D.; Beuermann, K.; Thomas, H.-C.; Graser, U.; Giommi, P.; Tagiaferri, G.
Affiliation:
AA(Louisiana State University, Baton Rouge), AB(Berlin, Technische Universitaet, Federal Republic of Germany), AC(Max-Planck-Institut fuer Physik und Astrophysik, Garching, Federal Republic of Germany), AD(Max-Planck-Institut fuer Astronomie, Heidelberg, Federal Republic of Germany), AE(EXOSAT Observatory, Noordwijk, Netherlands)
Journal:
Astronomy and Astrophysics (ISSN 0004-6361), vol. 239, no. 1-2, Nov. 1990, p. 260-264. (A&A Homepage)
Publication Date:
11/1990
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ABUNDANCE, EXOSAT SATELLITE, STELLAR SPECTRA, ULTRAVIOLET SPECTRA, WHITE DWARF STARS, HELIUM, IUE, STELLAR COMPOSITION, STELLAR MODELS, STELLAR TEMPERATURE
Bibliographic Code:
1990A&A...239..260K

Abstract

Exosat broad band filter observations, optical and IUE spectra, are presented for three DA white dwarfs. One source is a previously known Hyades white dwarf, the other two are new DA detected by Exosat. The results are consistent with previous observations of other DA white dwarfs and indicate that an absorber other than hydrogen (most probably helium) is present in the photosphere of these objects. From the present data, however, a distinction between the two possibilities (homogeneous vs stratified) is not possible.

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Title:
WW Horologii - Revised period and X-ray light curve
Authors:
Beuermann, K.; Thomas, H.-C.; Schwope, A. D.; Giommi, P.; Tagliaferri, G.
Affiliation:
AA(Berlin, Technische Universitaet; Max-Planck-Institut fuer Extraterrestrische Physik, Garching, Federal Republic of Germany), AB(Berlin, Technische Universitaet, Federal Republic of Germany), AC(Berlin, Technische Universitaet, Federal Republic of Germany), AD(EXOSAT Observatory, Noordwijk, Netherlands), AE(EXOSAT Observatory, Noordwijk, Netherlands)
Journal:
Astronomy and Astrophysics (ISSN 0004-6361), vol. 238, no. 1-2, Nov. 1990, p. 187-190. (A&A Homepage)
Publication Date:
11/1990
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
CATACLYSMIC VARIABLES, ECLIPSING BINARY STARS, LIGHT CURVE, WHITE DWARF STARS, X RAY SPECTRA, CHARGE COUPLED DEVICES, EXOSAT SATELLITE, MAGNETIC STARS, STELLAR MASS ACCRETION, STELLAR SPECTROPHOTOMETRY
Bibliographic Code:
1990A&A...238..187B

Abstract

An improved orbital period of the eclipsing AM Herculis binary WW Hor is reported, which allows the relative phasing of 1983 EXOSAT X-ray and the 1986-89 optical light curves to be established. It is found that X-rays and optical cyclotron continuum are produced by the same accreting pole on the magnetic white dwarf. In 1984, WW Hor was not detected with EXOSAT, suggesting that it experienced a low state of accretion.

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Title:
A study of BL Lacertae-type objects with Exosat. I - Flux correlations, luminosity variability, and spectral variability
Authors:
Giommi, P.; Barr, P.; Pollock, A. M. T.; Garilli, B.; Maccagni, D.
Affiliation:
AA(EXOSAT Observatory, Noordwijk, Netherlands), AB(EXOSAT Observatory, Noordwijk, Netherlands), AC(EXOSAT Observatory, Noordwijk, Netherlands), AD(CNR, Istituto di Fisica Cosmica, Milan, Italy), AE(CNR, Istituto di Fisica Cosmica, Milan, Italy)
Journal:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 356, June 20, 1990, p. 432-455. (ApJ Homepage)
Publication Date:
06/1990
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ASTRONOMICAL SPECTROSCOPY, BL LACERTAE OBJECTS, EXOSAT SATELLITE, LUMINOSITY, X RAY SOURCES, ABSORPTION SPECTRA, ACTIVE GALACTIC NUCLEI, LIGHT CURVE, SPECTRAL ENERGY DISTRIBUTION, SYNCHROTRON RADIATION
Bibliographic Code:
1990ApJ...356..432G

Abstract

Results are presented on a systematic analysis of more than 200 X-ray observations on 36 BL Lac objects, obtained from the Exosat archive, providing further strong evidence that the population of currently known BL Lac objects can be divided into two subclasses, Q-BL Lacs and X-BL Lacs. The subclass Q-BL Lacs includes most of the classical radio-discovered BL objects which are characterized by a continuum energy distribution, from radio to X-rays, similar to that of flat-radio-spectrum QSOs, highly polarized quasars, and optically violent variable QSOs. The subclass X-BL Lacs includes all the BL Lac objects which were detected in high-frequency surveys (i.e., optical and X-ray). This subclass is characterized by a very smooth energy distribution from radio to X-rays, which is often considered to be the signature of synchrotron emission.

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Title:
An X-ray flare observed from van Biesbroeck 8
Authors:
Tagliaferri, G.; Giommi, P.; Doyle, J. G.
Affiliation:
AA(EXOSAT Observatory, Noordwijk, Netherlands), AB(EXOSAT Observatory, Noordwijk, Netherlands), AC(Armagh Observatory, Northern Ireland)
Journal:
Astronomy and Astrophysics (ISSN 0004-6361), vol. 231, no. 1, May 1990, p. 131-133. (A&A Homepage)
Publication Date:
05/1990
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
EMISSION SPECTRA, STELLAR FLARES, STELLAR LUMINOSITY, X RAY SPECTRA, EXOSAT SATELLITE, FLARE STARS, HYDROGEN, INTERSTELLAR MATTER
Bibliographic Code:
1990A&A...231..131T

Abstract

An X-ray flare was detected on the previously unknown flare-star van Biesbroeck 8 ( = Gl 644 C). The total energy of the event in the 0.05-2 keV energy range was 8 x 10 to the 31st erg/s with a mean luminosity of 1.8 x 10 to 28th erg/s. This implies an emission measure of about 6 x 10 to the 50th/cu cm, and adopting a simple loop model an electron density of 10 to the 11th/cu cm or greater. It is estimated that the flare covered 1-4 percent of the stellar surface. Quiescent X-ray emission from VB 8 was detected during an Einstein-HRI observation. These properties of VB 8 suggest that stars later than M 5 can be very active X-ray emitters.

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Title:
Multifrequency observations of BL Lacertae
Authors:
Bregman, Joel N.; Glassgold, A. E.; Huggins, P. J.; Neugebauer, G.; Soifer, B. T.; Matthews, K.; Elias, J. H.; Webb, J. R.; Pollock, J. T.; Leacock, R. J.; Smith, A. G.; Aller, H. D.; Aller, M. F.; Hughes, P. A.; Maccagni, D.; Garilli, B.; Giommi, P.; Miller, J. S.; Stephens, S.; Balonek, T. J.; Dent, W. A.; Kinsel, W.; Wisniewski, W. Z.; Williams, P. M.; Brand, P. W. J. L.; Ku, W. H.-M.
Affiliation:
AA(New York University, NY; National Radio Astronomy Observatory, Charlottesville, VA), AB(New York University, NY; National Radio Astronomy Observatory, Charlottesville, VA), AC(New York University, NY; National Radio Astronomy Observatory, Charlottesville, VA), AD(Palomar Observatory, Pasadena, CA), AE(Palomar Observatory, Pasadena, CA)
Journal:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 352, April 1, 1990, p. 574-586. Research supported by the University of Massachusetts. (ApJ Homepage)
Publication Date:
04/1990
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
BL LACERTAE OBJECTS, INFRARED ASTRONOMY, RADIO ASTRONOMY, X RAY SPECTRA, LINE SPECTRA, SPECTRAL CORRELATION
Bibliographic Code:
1990ApJ...352..574B

Abstract

Optical, IR, and radio monitoring data covering 20 years are presented for BL Lac. Also, four simultaneous multifrequency spectra are given, covering the range 10 to the 9th - 10 to the 18th Hz. These spectra include ground-based observations and data from the Einstein, Exosat, IUE, and IRAS satellites. From the monitoring data, the character of emission variability is determined using structure functions. The multifrequency spectra are used to study the origin of X-ray emission and to determine the physical parameters of emitting regions. The data show that the emitting region is inhomogeneous, with a small inner region of high density and magnetic field that eventually becomes a large, partially opaque radio emitting region with a low density and magnetic fields. Also, the two simple predictions of the synchrotron self-Compton model are reproduced by the multifrequency spectra.

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Title:
AGN X-ray Variability with the EXOSAT Database
Authors:
Tagliaferri, G.; Barr, P.; Giommi, P.; Grandi, P.
Journal:
Bulletin of the American Astronomical Society, Vol. 22, p.805
Publication Date:
03/1990
Origin:
ADS
Bibliographic Code:
1990BAAS...22Q.805T

Abstract

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Title:
Bl-Lacertae Objects - One or Two Classes
Authors:
Garilli, B.; Maccagni, D.; Barr, P.; Giommi, P.; Pollock, A.
Journal:
Imaging X-Ray Astronomy. A Decade of Einstein Observatory Achievements. Editor, Martin Elvis; Publisher, Cambridge University Press, Cambridge, England, New York, 1990. LC # QB472.A1 I42 1990. ISBN # 0521381053. P.295, 1990
Publication Date:
00/1990
Origin:
ADS
Bibliographic Code:
1990ixra.conf..295G

Abstract

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Title:
The relationship between EXOSAT soft X-ray and Mt. Wilson CA II H+K flux densities
Authors:
Schrijver, C. J.; Giommi, P.; Dobson, A. K.; Radick, R. R.
Affiliation:
AA(ESTEC, Noordwijk, Netherlands), AB(ESTEC, Noordwijk, Netherlands), AC(Whitman College, Walla Walla, WA), AD(USAF, Geophysics Laboratory; National Solar Observatory, Sacramento Peak, NM)
Journal:
IN: Cool stars, stellar systems, and the sun; Proceedings of the 6th Cambridge Workshop, Seattle, WA, Sept. 18-21, 1989 (A91-44876 19-90). San Francisco, CA, Astronomical Society of the Pacific, 1990, p. 136-138.
Publication Date:
00/1990
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
CALCIUM, EXOSAT SATELLITE, FLUX DENSITY, H LINES, K LINES, X RAY SOURCES, ATMOSPHERIC HEATING, COOL STARS, SOUND WAVES, STELLAR ATMOSPHERES
Bibliographic Code:
1990csss....6..136S

Abstract

Data of Exosat soft X-ray fluxes, F(X), are compared to Mount Wilson Ca II H+K flux measurements, F(Ca), to assess the probability of nonradiatively heated atmospheres when coronal emissions cannot be observed. F(X) and F(Ca) have been observed within three days of each other in 13 stars and within 90 days in 8 stars, and the average interval for all but three stars is about 3 days. The Exosat data and the Einstein data are employed to relate F(X) and F(Ca) by means of a power law, which is consistent with the notion that X-ray fluxes are very low at the Ca II H+K lower limit flux.

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Title:
Rapid X ray variability in BL Lacertae objects
Authors:
Barr, P.; Giommi, P.; Pollock, A. M. T.; Garilli, B.; Maccagni, D.
Affiliation:
AA(European Space Agency. European Space Research and Technology Center, ESTEC, Noordwijk (Netherlands).), AB(European Space Agency. European Space Research and Technology Center, ESTEC, Noordwijk (Netherlands).), AC(European Space Agency. European Space Research and Technology Center, ESTEC, Noordwijk (Netherlands).), AD(Consiglio Nazionale delle Ricerche, Milan (Italy).), AE(Consiglio Nazionale delle Ricerche, Milan, Italy)
Journal:
In its The 23rd ESLAB Symposium on Two Topics in X Ray Astronomy. Volume 2: AGN and the X Ray Background p 831-835 (SEE N90-25841 19-89)
Publication Date:
11/1989
Category:
Space Radiation
Origin:
STI
NASA/STI Keywords:
BL LACERTAE OBJECTS, LIGHT CURVE, VARIABILITY, X RAY SPECTRA, EXOSAT SATELLITE, RED SHIFT, SATELLITE OBSERVATION, SPECTRUM ANALYSIS
Bibliographic Code:
1989ttxa.symp..831B

Abstract

A study of the short timescale X-ray variability of BL Lacertae objects is performed using the EXOSAT archive. Two hundred and one observations of 36 BL Lacertae objects revealed rapid variability in 21 observations of eight objects. Evidence for relativistic bulk motions is found in only one source PKS2155-304; 1E1402.3+0416 is also a candidate, its redshift being unknown. The other variable BL Lac objects exhibited less variations. Pronounced spectral changes were found, with the sources being harder when the intensity is higher.

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Title:
The optical characteristics of a sample of soft X ray selected active galactic nuclei
Authors:
Branduardi-Raymont, G.; Mittaz, J. P. D.; Mason, Keith O.; Puchnarewicz, E. M.; Murdin, P. G.; Allington-Smith, J. R.; Giommi, P.; Tagliaferri, G.; Angelini, Lorella
Affiliation:
AA(European Space Agency. European Space Research and Technology Center, ESTEC, Noordwijk, Netherlands), AB(European Space Agency. European Space Research and Technology Center, ESTEC, Noordwijk, Netherlands), AC(European Space Agency. European Space Research and Technology Center, ESTEC, Noordwijk, Netherlands), AD(European Space Agency. European Space Research and Technology Center, ESTEC, Noordwijk, Netherlands), AE(European Space Agency. European Space Research and Technology Center, ESTEC, Noordwijk, Netherlands), AF(European Space Agency. European Space Research and Technology Center, ESTEC, Noordwijk, Netherlands), AG(European Space Agency. European Space Research and Technology Center, ESTEC, Noordwijk, Netherlands), AH(European Space Agency. European Space Research and Technology Center, ESTEC, Noordwijk, Netherlands), AI(European Space Agency. European Space Research and Technology Center, ESTEC, Noordwijk, Netherlands)
Journal:
In ESA, The 23rd ESLAB Symposium on Two Topics in X Ray Astronomy. Volume 2: AGN and the X Ray Background p 713-717 (SEE N90-25841 19-89)
Publication Date:
11/1989
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
ACCRETION DISKS, ACTIVE GALACTIC NUCLEI, LUMINOSITY, X RAY SPECTRA, ASTRONOMICAL MODELS, EXOSAT SATELLITE, GALACTIC RADIATION, LIGHT (VISIBLE RADIATION), RED SHIFT
Bibliographic Code:
1989ttxa.symp..713B

Abstract

The optical characteristics of a sample of 30 active galactic nuclei (AGN), discovered in EXOSAT CMA fields at high galactic latitude, are discussed. Optical spectra were obtained in the course of the identification work in 1988 and 1989. The data was reduced in a uniform fashion and fitted with multicomponent model spectra. Particular care was used in identifying and modeling the variety of Fe multiplets present in the wavelength band under consideration. Preliminary results of this work in terms of redshift and luminosity distributions, soft X-ray to optical luminosity ratio, and line strengths versus soft X-ray luminosity are discussed.

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Title:
A Systematic Study of AGN X-ray Variability Using the EXOSAT Database
Authors:
Giommi, P.; Barr, P.; Tagliaferri, G.; Grandi, P.
Journal:
Bulletin of the American Astronomical Society, Vol. 21, p.1130
Publication Date:
09/1989
Origin:
ADS
Bibliographic Code:
1989BAAS...21.1130G

Abstract

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Title:
EXOSAT observations of five luminous globular cluster X-ray sources
Authors:
Parmar, A. N.; Stella, L.; Giommi, P.
Affiliation:
AA(EXOSAT Observatory, Noordwijk, Netherlands), AB(EXOSAT Observatory, Noordwijk, Netherlands), AC(EXOSAT Observatory, Noordwijk, Netherlands)
Journal:
Astronomy and Astrophysics (ISSN 0004-6361), vol. 222, no. 1-2, Sept. 1989, p. 96-102. (A&A Homepage)
Publication Date:
09/1989
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
EXOSAT SATELLITE, GLOBULAR CLUSTERS, LIGHT CURVE, NEUTRON STARS, SATELLITE OBSERVATION, X RAY BINARIES, ACCRETION DISKS, STELLAR MASS
Bibliographic Code:
1989A&A...222...96P

Abstract

Exosat observations are used to search for orbital modulations in the X-ray light curves of five luminous globular cluster X-ray sources in NGC 1851, NGC 6441, NGC 6712, Terzan 1, and Terzan 2. Upper limits to possible short-period orbital modulation are presented. Two or three intensity dips are observed in the light curve of NGC 6441. The results suggest that these dips are similar to those observed from X 1755-338. It is found that, if the dips are periodic, they result from obscuration of an extended accretion disk corona that contributes more than 15 percent of the observed flux, or from obscuration of the central neutron star by material that is significantly photoionized.

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Title:
EXO 032957-2606.9 - A new long-period probable AM Herculis binary
Authors:
Beuermann, K.; Thomas, H.-C.; Giommi, P.; Tagliaferri, G.; Schwope, A. D.
Affiliation:
AA(Berlin, Technische Universitaet; Max-Planck-Institut fuer extraterrestrische Physik, Garching, Federal Republic of Germany), AB(Max-Planck-Institut fuer Physik und Astrophysik, Garching, Federal Republic of Germany), AC(EXOSAT Observatory, Noordwijik, Netherlands), AD(EXOSAT Observatory, Noordwijik, Netherlands), AE(Berlin, Technische Universitaet, Federal Republic of Germany)
Journal:
Astronomy and Astrophysics (ISSN 0004-6361), vol. 219, no. 1-2, July 1989, p. L7-L10. (A&A Homepage)
Publication Date:
07/1989
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
CATACLYSMIC VARIABLES, STELLAR SPECTROPHOTOMETRY, X RAY SOURCES, EMISSION SPECTRA, EXOSAT SATELLITE, SPECTRAL LINE WIDTH, STELLAR ORBITS, VISIBLE SPECTRUM
Bibliographic Code:
1989A&A...219L...7B

Abstract

The identification of the serendipitous Exosat X-ray source EXO032957-2606.9 with a new probable long-period AM Herculis binary is reported. The orbital period is (228 + or - 1) min (1-sigma error). The classification as an AM Herculis binary is based on the very soft X-ray spectrum and the characteristics of the high-excitation optical spectrum. The spectrum is peculiar in that the radial-velocity amplitude is only 60 km/s and the line profiles exhibit persistent blue wings extending to -1000 km/s. The inclination of the system is small, and the prime accreting pole is permanently hidden from view. The variable soft X-ray flux originates from the second pole which faces the observer. Systems with such geometry are expected to exist and EXO032957-2606.9 would be the first to be identified. The secondary star was detected by its TiO bands and is approximately of spectral type dM4.5. The distance to the system is about 520 pc.

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Title:
Discovery of a BL Lacertae object (EXO 055625-3838.6) in the error box of H0557-385
Authors:
Giommi, P.; Beuermann, K.; Barr, P.; Schwope, A.; Tagliaferri, G.; Thomas, H. C.
Affiliation:
AA(EXOSAT Observatory, Noordwijk, Netherlands), AB(EXOSAT Observatory, Noordwijk, Netherlands), AC(EXOSAT Observatory, Noordwijk, Netherlands), AD(Berlin, Technische Universitaet; Max-Planck-Institut fuer Extraterrestrische Physik, Garching, Federal Republic of Germany), AE(Berlin, Technische Universitaet, Federal Republic of Germany)
Journal:
Royal Astronomical Society, Monthly Notices (ISSN 0035-8711), vol. 236, Jan. 15, 1989, p. 375-383. (MNRAS Homepage)
Publication Date:
01/1989
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ASTRONOMICAL SPECTROSCOPY, BL LACERTAE OBJECTS, X RAY SOURCES, ERROR ANALYSIS, EXOSAT SATELLITE, LIGHT CURVE, SEYFERT GALAXIES, VISIBLE SPECTRUM
Bibliographic Code:
1989MNRAS.236..375G

Abstract

X-ray and optical data reveal a new BL Lac object (EXO 055625-3838.6) within the error box of H0557-385. The long-term hard X-ray light curve of H0557-385 is found to vary by factor of not less than 10. It is noted that the reclassification as BL Lacs of even a very small number of the HEAO1 survey sources would suggest that the previous estimate of the space density of these objects at fluxes of greater than 10 to the -11th erg/sq cm per s should be substantially increased.

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Title:
Variability of a Sample of X-Ray Selected BL-Lacs
Authors:
Grandi, P.; Giommi, P.; Palumbo, C. G. G.; Tagliaferri, G.
Journal:
Proceedings of the 21st International Cosmic Ray Conference. Volume 1 (OG Sessions), p.10
Publication Date:
00/1989
Origin:
ADS
Bibliographic Code:
1989ICRC....1...10G

Abstract

Not Available

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Title:
An X-Ray Spectral Survey of BL Lac Objects
Authors:
Barr, P.; Giommi, P.; Pollock, A.; Tagliaferri, G.; Maccagni, D.; Garilli, B.
Journal:
Active Galactic Nuclei: proceedings of the 134th Symposium of the International Astronomical Union, held in Santa Cruz, California, August 15-19, 1988. Edited by Donald E. Osterbrock and Joseph S. Miller. International Astronomical Union. Symposium no. 134, Kluwer Academic Publishers, Dordrecht, p.191
Publication Date:
00/1989
Origin:
ADS
Bibliographic Code:
1989IAUS..134..191B

Abstract

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Title:
The EXOSAT Spectral Survey of Bl-Lacertae Objects
Authors:
Barr, P.; Giommi, P.; Pollock, A.; Tagliaferri, G.; Maccagni, D.; Garilli, B.
Journal:
BL Lac Objects. Proceedings of a workshop held in Como, Italy, September 20-23, 1988. Editors, L. Maraschi, T. Maccacaro, M.-H. Ulrich; Publisher, Springer-Verlag, Berlin, New York, NY, 1989. LC # QB858.35 .B5 1989. ISBN: 0-387-51389-2. P. 290, 1989
Publication Date:
00/1989
Origin:
ADS
Bibliographic Code:
1989blo..conf..290B

Abstract

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Title:
Bl-Lacertae Objects as X-Ray Sources - the EXOSAT Observations
Authors:
Maccagni, D.; Garilli, B.; Barr, P.; Giommi, P.; Pollock, A.
Journal:
BL Lac Objects. Proceedings of a workshop held in Como, Italy, September 20-23, 1988. Editors, L. Maraschi, T. Maccacaro, M.-H. Ulrich; Publisher, Springer-Verlag, Berlin, New York, NY, 1989. LC # QB858.35 .B5 1989. ISBN: 0-387-51389-2. P. 281, 1989
Publication Date:
00/1989
Origin:
ADS
Bibliographic Code:
1989blo..conf..281M

Abstract

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Title:
Discovery of an X-Ray Selected Optically Highly Variable Quasar
Authors:
Raymont, G. Branduardi; Mason, K. O.; Mittaz, J. P. D.; Murdin, P. G.; Allington-Smith, J. R.; Giommi, P.; Tagliaferri, G.; Angelini, L.
Journal:
BL Lac Objects. Proceedings of a workshop held in Como, Italy, September 20-23, 1988. Editors, L. Maraschi, T. Maccacaro, M.-H. Ulrich; Publisher, Springer-Verlag, Berlin, New York, NY, 1989. LC # QB858.35 .B5 1989. ISBN: 0-387-51389-2. P. 261, 1989
Publication Date:
00/1989
Origin:
ADS
Bibliographic Code:
1989blo..conf..261B

Abstract

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Title:
Two New Bl-Lacertae Objects Discovered in the Error Boxes of Hard X-Ray Sources
Authors:
Tagliaferri, G.; Giommi, P.; Beuermann, K.; Raymont, G. Branduardi; Brissenden, R.; Mason, K. O.; Murdin, P.; Thomas, H. C.; Tuohy, I.
Journal:
BL Lac Objects. Proceedings of a workshop held in Como, Italy, September 20-23, 1988. Editors, L. Maraschi, T. Maccacaro, M.-H. Ulrich; Publisher, Springer-Verlag, Berlin, New York, NY, 1989. LC # QB858.35 .B5 1989. ISBN: 0-387-51389-2. P. 257, 1989
Publication Date:
00/1989
Origin:
ADS
Bibliographic Code:
1989blo..conf..257T

Abstract

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Title:
Bl-Lacertae Objects from the EXOSAT High Galactic Latitude Survey - Constraints on the Logn-Logs and on the Cosmological Evolution
Authors:
Giommi, P.; Tagliaferri, G.; Beuermann, K.; Raymont, G. Branduardi; Brissenden, R.; Graser, U.; Mason, K. O.; Murdin, P.; Pooley, G.; Thomas, H. C.; Tuohy, I.
Journal:
BL Lac Objects. Proceedings of a workshop held in Como, Italy, September 20-23, 1988. Editors, L. Maraschi, T. Maccacaro, M.-H. Ulrich; Publisher, Springer-Verlag, Berlin, New York, NY, 1989. LC # QB858.35 .B5 1989. ISBN: 0-387-51389-2. P. 231, 1989
Publication Date:
00/1989
Origin:
ADS
Bibliographic Code:
1989blo..conf..231G

Abstract

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Title:
EXO 032957-2606.9
Authors:
Beuermann, K.; Thomas, H.-C.; Giommi, P.; Tagliaferri, G.
Journal:
IAU Circ., 4671, 1 (1988). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
11/1988
Origin:
CBAT
Objects:
EXO 032957-2606.9
Bibliographic Code:
1988IAUC.4671....1B

Abstract

IAUC 4671 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
An Overview of the EXOSAT Database
Authors:
White, N. E.; Giommi, P.; Parmar, A. N.; Angelini, L.; Tagliaferri, G.; Osborne, J.; Stella, L.; Pollock, A.; Barr, P.; Haberl, F.
Journal:
Bulletin of the American Astronomical Society, Vol. 20, p.1035
Publication Date:
09/1988
Origin:
ADS
Bibliographic Code:
1988BAAS...20.1035W

Abstract

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Title:
The EXOSAT Results Database
Authors:
Giommi, P.; Parmar, A. N.; White, N. E.; Angelini, L.; Barr, P.; Haberl, F.; Gottwald, M.; van der Klis, M.; Osborne, J.; Pollock, A. M. T.; Stella, L.; Tagliaferri, G.
Journal:
Bulletin of the American Astronomical Society, Vol. 20, p.1035
Publication Date:
09/1988
Origin:
ADS
Bibliographic Code:
1988BAAS...20.1035G

Abstract

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Title:
Variability in the Steep X-ray Spectrum of the Quasar PG1211+143
Authors:
Elvis, M.; Giommi, P.; McDowell, J.; Wilkes, B.
Journal:
Bulletin of the American Astronomical Society, Vol. 20, p.1024
Publication Date:
09/1988
Origin:
ADS
Bibliographic Code:
1988BAAS...20.1024E

Abstract

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Title:
An X-ray flare from a B9 + post-T Tauri star system in the field of the Seyfert Galaxy III ZW 2
Authors:
Tagliaferri, G.; Giommi, P.; Angelini, L.; Osborne, J. P.; Pallavicini, R.
Affiliation:
AA(EXOSAT Observatory, Noordwijk, Netherlands), AB(EXOSAT Observatory, Noordwijk, Netherlands), AC(EXOSAT Observatory, Noordwijk, Netherlands), AD(EXOSAT Observatory, Noordwijk, Netherlands), AE(Arcetri, Osservatorio Astrofisico, Florence, Italy)
Journal:
Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 331, Aug. 15, 1988, p. L113-L116. (ApJ Homepage)
Publication Date:
08/1988
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
PRE-MAIN SEQUENCE STARS, SEYFERT GALAXIES, STELLAR FLARES, STELLAR SPECTRA, X RAY SOURCES, BINARY STARS, EXOSAT SATELLITE, LATE STARS, LIGHT CURVE, T TAURI STARS
Bibliographic Code:
1988ApJ...331L.113T

Abstract

The serendipitous detection of X-ray emission from the visual binary HD 560, consisting of a B-type primary and a later-type secondary, is reported. This system was seen in the field of the Seyfert type I galaxy III Zw 2, which was observed four times by Exosat. During one of these observations, the serendipitous source was observed to flare in both low-energy and medium-energy experiments. It is shown here that the observed variability was entirely due to the serendipitous source. It is argued that virtually all of the X-ray flux from the binary came from this late-type component, and that this component is probably a post-T Tauri star.

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Title:
The discovery of the 2 hour modulated X-ray source EXO 033319-2554.2, an AM Herculis system
Authors:
Osborne, J. P.; Giommi, P.; Angelini, L.; Tagliaferri, G.; Stella, L.
Affiliation:
AA(EXOSAT Observatory, Noordwijk, Netherlands), AB(EXOSAT Observatory, Noordwijk, Netherlands), AC(EXOSAT Observatory, Noordwijk, Netherlands), AD(EXOSAT Observatory, Noordwijk, Netherlands), AE(EXOSAT Observatory, Noordwijk, Netherlands)
Journal:
Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 328, May 15, 1988, p. L45-L50. (ApJ Homepage)
Publication Date:
05/1988
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
MAGNETIC STARS, STELLAR MASS ACCRETION, WHITE DWARF STARS, X RAY BINARIES, X RAY SOURCES, EXOSAT SATELLITE, MODULATION, STELLAR LUMINOSITY
Bibliographic Code:
1988ApJ...328L..45O

Abstract

The discovery of EXO 033319-2554.2, a soft X-ray source modulated at a period of about 128 minutes, is reported. The bright part of the cycle lasts 0.55 in phase and is cut by an eclipse-like feature lasting eight minutes, with unresolved ingress and egress 0.13 after maximum intensity. The soft X-ray color requires blackbody temperatures less than 25 eV. The optical counterpart has a magnitude m(v) of roughly 18.5. These data imply that the object is an AM Her system.

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Title:
The detection of a high-energy break in the X-ray spectrum of the BL Lacertae object PKS 0548-32
Authors:
Barr, P.; Giommi, P.; Maccagni, D.
Affiliation:
AA(EXOSAT Observatory, Noordwijk, Netherlands), AB(EXOSAT Observatory, Noordwijk, Netherlands), AC(CNR, Istituto di Fisica Cosmica, Milan, Italy)
Journal:
Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X), vol. 324, Jan. 1, 1988, p. L11-L15. (ApJ Homepage)
Publication Date:
01/1988
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ABSORPTION SPECTRA, ASTRONOMICAL MODELS, BL LACERTAE OBJECTS, SPECTRAL ENERGY DISTRIBUTION, X RAY SPECTRA, BREMSSTRAHLUNG, ELECTRON-POSITRON PAIRS, EXOSAT SATELLITE, PLASMA SPECTRA, SYNCHROTRON RADIATION
Bibliographic Code:
1988ApJ...324L..11B

Abstract

The results of a deep Exosat observation of the BL Lac object PKS 0548-32 performed in March 1986 are presented. The 0.05-10-keV X-ray spectrum is characterized by a relatively flat (power-law energy spectral index alpha = about 0.9) continuum below 5 keV which steepens at higher energies. There is no evidence for any excess absorption intrinsic to the BL Lac object itself. With the exception of two observations made in 1977 and 1978 (when PKS 0548-32 was unusually bright), all previous measurements of the X-ray spectrum of this source are consistent with the spectral form identified by Exosat. Although emission from an electron-positron pair plasma with compactness parameter of about 100 can reproduce the observed Exosat spectrum, difficulties arise in explaining the presence of a high-energy tail in 1977. If the X-ray emission arises via the synchrotron process with the spectral break due to radiative losses, reacceleration of the emitting particles and an inhomogeneous emission region are indicated.

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Title:
A Giant X-Ray Flare from a B9+ POST T-Tauri System Detected by EXOSAT
Authors:
Tagliaferri, G.; Giommi, P.; Angelini, L.; Osborne, J. P.; Pallavicini, R.
Journal:
SOLAR AND STELLAR FLARES: I.A.U. COLL.104 P.131, 1988
Publication Date:
00/1988
Origin:
KNUDSEN
Bibliographic Code:
1988sasf.conf..131T

Abstract

Not Available

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Title:
Serendipitous sources in EXOSAT images
Authors:
Giommi, P.; Tagliaferri, G.; Angelini, L.
Affiliation:
AA(Exosat Observatory, Noordwijk, Netherlands; CNR, Istituto di Fisica Cosmica, Milan, Italy), AB(Exosat Observatory, Noordwijk, Netherlands), AC(Exosat Observatory, Noordwijk, Netherlands)
Journal:
Societa Astronomica Italiana, Memorie (ISSN 0037-8720), vol. 59, no. 1-2, 1988, p. 33-51.
Publication Date:
00/1988
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
EXOSAT SATELLITE, SKY SURVEYS (ASTRONOMY), X RAY IMAGERY, X RAY SOURCES, BL LACERTAE OBJECTS, CATACLYSMIC VARIABLES, GALACTIC STRUCTURE, LATE STARS, LUMINOSITY, SEYFERT GALAXIES
Bibliographic Code:
1988MmSAI..59...33G

Abstract

Preliminary results are presented from the analysis of a sample of over 500 sources serendipitously detected by the imaging instruments on the Exosat satellite. The sources, which belong to several classes of X-ray emitters, are used to study the spatial distribution, the X-ray slope, and the luminosity variability of celestial objects. The results of the Exosat High Galactic Latitude Survey are compared with those of the Einstein Extended Medium Sensitivity Survey (Gioia et al., 1986). The correlation of the sky position of extragalactic sources with the amount of galactic NH shows that the average energy spectral index of extragalacitc sources in the 0.05-3.5 keV band is steeper than 1. Also, rapid and large amplitude X-ray luminosity variability is detected in late-type stars, cataclysmic variables, Seyfert galaxies and BL Lacertae objects.

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Title:
X-ray time variability and luminosity correlations in BL Lacertae objects
Authors:
Giommi, P.; Barr, P.; Pollock, A.; Garilli, B.; Maccagni, D.
Affiliation:
AA(EXOSAT Observatory, Noordwijk, Netherlands), AB(EXOSAT Observatory, Noordwijk, Netherlands), AC(EXOSAT Observatory, Noordwijk, Netherlands), AD(CNR, Istituto di Fisica Cosmica, Milan, Italy), AE(CNR, Istituto di Fisica Cosmica, Milan, Italy)
Journal:
(COSPAR and IAU, Symposium on the Physics of Compact Objects, Sofia, Bulgaria, July 13-18, 1987) Advances in Space Research (ISSN 0273-1177), vol. 8, no. 2-3, 1988, p. 79-83. (AdSpR Homepage)
Publication Date:
00/1988
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
ACTIVE GALACTIC NUCLEI, BL LACERTAE OBJECTS, GALACTIC RADIO WAVES, RADIANT FLUX DENSITY, X RAY SOURCES, EXOSAT SATELLITE, QUASARS, RED SHIFT, SEYFERT GALAXIES
Bibliographic Code:
1988AdSpR...8...79G

Abstract

The preliminary results of a study of the soft X-ray properties of a sample of 34 BL Lacertae objects observed with the Exosat observatory are presented. Strong correlations between the X-ray, optical, and radio fluxes have been found in the subsample of X-ray selected objects. X-ray variability is common and has been significantly detected in 14 (8 X-ray-selected and 6 radio-selected) out of the 25 objects observed more than once. Flux variations by up to a factor 5 have been found. The commonest form of variability encountered consists of small amplitude variations about a quiescent flux level whose mean value remains roughly constant over time scales of years.

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Title:
EXO 033319-2554.2
Authors:
Giommi, P.; Angelini, L.; Osborne, J.; Stella, L.; Tagliaferri, G.; Beuermann, K.; Thomas, H.-C.
Journal:
IAU Circ., 4486, 1 (1987). Edited by Green, D. W. E. (IAUC Homepage)
Publication Date:
11/1987
Origin:
CBAT
Objects:
EXO 033319-2554.2
Bibliographic Code:
1987IAUC.4486....1G

Abstract

IAUC 4486 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
X-ray and optical observations of X-ray-selected BL Laceratae objects
Authors:
Giommi, P.; Barr, P.; Garilli, B.; Gioia, I. M.; Maccacaro, T.; Maccagni, D.; Schild, R. E.
Affiliation:
AA(EXOSAT Observatory, Noordwijk, Netherlands), AB(EXOSAT Observatory, Noordwijk, Netherlands), AC(CNR, Istituto di Fisica Cosmica, Milan, Italy), AD(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AE(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA)
Journal:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 322, Nov. 15, 1987, p. 662-672. ESA-CNR-supported research. (ApJ Homepage)
Publication Date:
11/1987
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
BL LACERTAE OBJECTS, LIGHT CURVE, X RAY SOURCES, EXOSAT SATELLITE, MONTE CARLO METHOD, STELLAR LUMINOSITY, X RAY ASTRONOMY
Bibliographic Code:
1987ApJ...322..662G

Abstract

Results from several X-ray and optical observations of five X-ray-selected BL Lacertae objects are reported. X-ray light curves covering periods of up to 6 yr reveal that the X-ray flux from these objects does not show large-amplitude trends over this time scale. Variations of up to 2 mag have been observed in the optical. The soft X-ray spectra of three objects have been measured with the Exosat Medium Energy detectors. Energy spectral indices range between one and two. In one case (1E 1415.6 + 2557), evidence for photoelectric absorption in excess of that due to the local interstellar medium has been found. A new optical flare from 1E 1402.3 + 0416, with rise and decay time of order of a few weeks, has been detected.

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Title:
EXOSAT results on the dMe flare Star Wolf 630AB and on VB 8
Authors:
Tagliaferri, G.; White, N. E.; Giommi, P.
Affiliation:
Colorado Univ., Boulder.
Journal:
In its 5th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun 1 p (SEE N88-13092 04-89)
Publication Date:
07/1987
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
EXOSAT SATELLITE, FLARE STARS, HEAO 2, HIGH RESOLUTION, INFRARED DETECTORS, STELLAR FLARES, X RAY SPECTRA, FLUX DENSITY, MODELS, PLASMAS (PHYSICS), SPECTRUM ANALYSIS, X RAY ASTRONOMY
Bibliographic Code:
1987coss.workQ....T

Abstract

Results from three X-ray observations of Wolf 630AB obtained from the Exosat archive are reported. Two flares have been detected in both the LE and ME experiments. In one case the source flux is sufficiently high to allow a spectral analysis. The Raymond-Smith plasma model gives an acceptable fit to the rise and fall phase with temperatures of 4.3 and 2.5 keV, respectively. During the March 1985 observation a 15 minute flare was detected from the nearby star VB 8 (about 4 arcmin far from Wolf 630AB). Combining Exosat and Einstein HRI data constrains the temperature of the quiescent X-ray emission to be higher than .13 KeV.

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Title:
A 25 min modulation from the vicinity of the unusually soft X-ray source X0142+614
Authors:
White, N. E.; Mason, K. O.; Giommi, P.; Angelini, L.; Pooley, G.; Branduardi-Raymont, G.; Murdin, P. G.; Wall, J. V.
Affiliation:
AA(EXOSAT Observatory, Noordwijk, Netherlands), AB(EXOSAT Observatory, Noordwijk, Netherlands), AC(EXOSAT Observatory, Noordwijk, Netherlands), AD(London, University College, Dorking, England), AE(Mullard Radio Astronomy Observatory, Cambridge, England)
Journal:
Royal Astronomical Society, Monthly Notices (ISSN 0035-8711), vol. 226, June 1, 1987, p. 645-654. (MNRAS Homepage)
Publication Date:
06/1987
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ENERGY SPECTRA, PERIODIC VARIATIONS, PULSE AMPLITUDE, SPECTRUM ANALYSIS, X RAY SOURCES, EXOSAT SATELLITE, HEAO 2, NEUTRON STARS, RADIO ASTRONOMY, X RAY ABSORPTION
Bibliographic Code:
1987MNRAS.226..645W

Abstract

The results of three Exosat observations of X0142+614 made in August 1984 and November and December 1985 are reported. A 25-min coherent modulation was detected during the first observation, but not during the following two. The modulation peak-to-peak amplitude was 55 percent between 3 and 8 keV and less than 1 percent between 1 and 3 keV. The 1-10-keV spectrum was fit with a power law of energy index about 3 in all three observations, except during the observation when X-ray pulsations were detected, when a second power-law component with an energy index of about 1 and a high absorption column density was also required. The data are consistent with the modulation being confined to the flatter spectral component. New position measurements from both Exosat and the Einstein HRI are presented, and a search has been made for an optical counterpart to the X-ray source; no candidate star brigher than R = about 22.5 was found. A radio map of the vicinity of the X-ray source at 5 GHz yielded an upper limit of 5 mJy. The X-ray spectrum is absorbed by the equivalent of 1.5 x 10 to the 22nd H/sq cm which, if interstellar, would cause five magnitudes of extinction in the R-band. The X-ray properties of X0142+614 do not resemble those of any other Galactic or extragalactic X-ray source, and its nature is puzzling.

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Title:
EXO 023432-5232.3 - A new 114-minute probable AM-Herculis-type binary
Authors:
Beuermann, K.; Thomas, H. C.; Giommi, P.; Tagliaferri, G.
Affiliation:
AA((Berlin, Technische Universitaet; Max-Planck-Institut fuer Extraterrestrische Physik, Garching, West), AB((Berlin, Technische Universitaet; Max-Planck-Institut fuer Extraterrestrische Physik, Garching, West), AC((EXOSAT Observatory, Noordwijk, Netherlands)), AD((EXOSAT Observatory, Noordwijk, Netherlands))
Journal:
Astronomy and Astrophysics (ISSN 0004-6361), vol. 175, no. 1-2, March 1987, p. L9-L12. (A&A Homepage)
Publication Date:
03/1987
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
CATACLYSMIC VARIABLES, STELLAR SPECTROPHOTOMETRY, X RAY BINARIES, CYCLOTRON RADIATION, EXOSAT SATELLITE, PERIODIC VARIATIONS, STELLAR SPECTRA, WHITE DWARF STARS, X RAY SPECTRA
Bibliographic Code:
1987A&A...175L...9B

Abstract

A new probable AM Herculis binary was found in the course of an optical identification program of serendipitous X-ray sources detected with the Exosat satellite. Spectrophotometry of the 19-mag optical counterpart shows that it carries most of the hallmarks of AM Herculis binaries. The orbital period is 114.6 minutes, and makes it the sixth AM Her star in the small period range of 113 to 115 minutes. The system is at a probable distance of 300-500 pc. The space density of AM Herculis binaries is discussed.

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Title:
X-ray studies of quasars with the Einstein Observatory. IV - X-ray dependence on radio emission
Authors:
Worrall, D. M.; Tananbaum, H.; Giommi, P.; Zamorani, G.
Affiliation:
AA(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AB(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AC(EXOSAT Observatory, Darmstadt, West Germany), AD(CNR, Istituto di Radioastronomia, Bologna, Italy)
Journal:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 313, Feb. 15, 1987, p. 596-606. Research supported by the Smithsonian Institution and CNR. (ApJ Homepage)
Publication Date:
02/1987
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
QUASARS, RADIO EMISSION, SPACEBORNE ASTRONOMY, X RAY ASTRONOMY, ASTRONOMICAL CATALOGS, DATA SAMPLING, HEAO 2, LUMINOSITY, STATISTICAL ANALYSIS
Bibliographic Code:
1987ApJ...313..596W

Abstract

The X-ray properties of a sample of 114 radio-loud quasars observed with the Einstein Observatory are examined, and the results are compared with those obtained from a large sample of radio-quiet quasars. The results of statistical analysis of the dependence of X-ray luminosity on combined functions of optical and radio luminosity show that the dependence on both luminosities is important. However, statistically significant differences are found between subsamples of flat radio spectra quasars and steep radio spectra quasars with regard to dependence of X-ray luminosity on only radio luminosity. The data are consistent with radio-loud quasars having a physical component, not directly related to the optical luminosity, which produces the core radio luminosity plus 'extra' X-ray emission.

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Title:
Rapid X-Ray Variability in the Seyfert Galaxy NGC4593
Authors:
Barr, P.; Clavel, J.; Giommi, P.; Mushotzky, R. F.; Madejski, G.
Journal:
Variability of Galactic and Extragalactic X-Ray Sources. Proceedings of an International Symposium held in Villa Olmo, Como, Italy, October 20-22, 1986. Editor, Aldo Treves; Publisher, Associazione Per l'Avanzamento Dell'Astronomia, Milano, Italy, 1987. CALL # QB472.A1 V37 1987. ISBN # NONE. P. 43, 1987
Publication Date:
00/1987
Origin:
ADS
Bibliographic Code:
1987vgeg.conf...43B

Abstract

Not Available

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Title:
The EXOSAT high galactic latitude survey
Authors:
Giommi, P.; Tagliaferri, G.
Affiliation:
AA(EXOSAT Observatory, Darmstadt, Federal Republic of Germany), AB(EXOSAT Observatory, Darmstadt, Federal Republic of Germany)
Journal:
IN: Observational cosmology; Proceedings of the IAU Symposium, Beijing, People's Republic of China, Aug. 25-30, 1986 (A88-29629 11-90). Dordrecht, D. Reidel Publishing Co., 1987, p. 601-605.
Publication Date:
00/1987
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
EXOSAT SATELLITE, X RAY IMAGERY, X RAY SOURCES, ACTIVE GALACTIC NUCLEI, HYDROGEN
Bibliographic Code:
1987IAUS..124..601G

Abstract

A survey of about 570 square degrees of high galactic latitude sky was performed using a large number of Exosat X-ray images. A total of 130 serendipitous sources were detected and about 60 percent of them have been identified with cataloged objects. The large majority of the remaining sources have faint optical counterparts on POSS or ESO plates and are expected to be extragalactic. The comparison of the results with those of the Einstein Medium Sensitivity Survey and an analysis of the correlation between the spatial distribution of Exosat serendipitous sources and the amount of galactic hydrogen column density indicate that the average spectral index of extragalactic X-ray sources is steeper than the canonical AGN slope.

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Title:
X-Ray and Optical Observations of the Flare Star Wolf 630 AB and of VB 8
Authors:
Tagliaferri, G.; White, N. E.; Giommi, P.; Doyle, J. G.
Journal:
Cool Stars, Stellar Systems and the Sun, Proceedings of the Fifth Cambridge Workshop held in Boulder, Colo., 8-11 Jul. 1987. Lecture Notes in Physics, Vol. 291, edited by J. L. Linsky and R. E. Stencel. Springer-Verlag, Berlin, 1987., p.176
Publication Date:
00/1987
Origin:
ADS
Bibliographic Code:
1987csss....5..176T

Abstract

Not Available

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Title:
EXO 023432-5232.3
Authors:
Beuermann, K.; Thomas, H.-C.; Giommi, P.; Tagliaferri, G.
Journal:
IAU Circ., 4289, 2 (1986). Edited by Marsden, B. G. (IAUC Homepage)
Publication Date:
12/1986
Origin:
CBAT
Objects:
EXO 023432-5232.3
Bibliographic Code:
1986IAUC.4289....2B

Abstract

IAUC 4289 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
Multifrequency observations of the Blazar PKS 0537-441 in a moderately active state
Authors:
Tanzi, E. G.; Barr, P.; Bouchet, P.; Chiappetti, L.; Cristiani, S.; Falomo, R.; Giommi, P.; Maraschi, L.; Treves, A.
Affiliation:
AA(CNR, Istituto di Fisica Cosmica, Milan, Italy), AB(CNR, Istituto di Fisica Cosmica, Milan, Italy), AC(EXOSAT Observatory, Darmstadt, West Germany), AD(European Southern Observatory, La Silla, Chile), AE(European Southern Observatory, La Silla, Chile)
Journal:
Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X), vol. 311, Dec. 1, 1986, p. L13-L16. (ApJ Homepage)
Publication Date:
12/1986
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
ASTRONOMICAL PHOTOMETRY, BL LACERTAE OBJECTS, BLAZARS, SPECTROPHOTOMETRY, EXOSAT SATELLITE, INFRARED PHOTOMETRY, IUE, LIGHT CURVE, ULTRAVIOLET SPECTRA, VISIBLE SPECTRUM, X RAY SPECTRA
Bibliographic Code:
1986ApJ...311L..13T

Abstract

PKS 0537-441 was observed during an active state in February 1985 at infrared, optical, UV, and X-ray frequencies. Comparison with earlier measurements indicates that the source brightened by a factor of approximately 2 in all bands. This suggests that the same spatial region may be responsible for the emission in the whole spectral range observed.

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Title:
H 1504 + 65 - an extraordinarily hot compact star devoid of hydrogen and helium
Authors:
Nousek, J. A.; Shipman, Harry L.; Holberg, J. B.; Liebert, James; Pravdo, Steven H.; White, N. E.; Giommi, Paolo
Affiliation:
AA(Pennsylvania State University, University Park), AB(Delaware, University, Newark), AC(Arizona, University; Steward Observatory, Tucson, AZ), AD(Arizona, University; Steward Observatory, Tucson, AZ), AE(California Institute of Technology, Jet Propulsion Laboratory, Pasadena, CA)
Journal:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 309, Oct. 1, 1986, p. 230-240. NASA-supported research. (ApJ Homepage)
Publication Date:
10/1986
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
HOT STARS, STELLAR COMPOSITION, STELLAR SPECTROPHOTOMETRY, ULTRAVIOLET SPECTRA, WHITE DWARF STARS, X RAY STARS, HELIUM, HYDROGEN, METALLIC STARS, STELLAR TEMPERATURE
Bibliographic Code:
1986ApJ...309..230N

Abstract

The optical identification of the bright soft X-ray source H 1504 + 65, originally discovered by the HEAO I A-2 low energy detectors, is reported. The optical counterpart exhibits a steep, virtually featureless continuum from optical wavelengths through the ultraviolet. The spectrum is remarkably featureless except for a broad O VI adsorption feature at 3494.7 A and C IV absorption at 3934 A and emission at 4658 A. The soft X-ray data, which are not consistent with any published models for degenerate stars having predominantly H or He compositions, suggest that H 1504 + 65 is a metal-rich, near-degenerate object of very high temperature. Qualitative considerations indicate that it is definitely hotter than PG 1159 - 035 and similar objects. A temperature of roughly 160,000 K is suggested.

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Title:
The EXOSAT High Galactic latitude Survey
Authors:
Giommi, P.; Tagliaferri, G.
Journal:
Bulletin of the American Astronomical Society, Vol. 18, p.1040
Publication Date:
09/1986
Origin:
ADS
Bibliographic Code:
1986BAAS...18.1040G

Abstract

Not Available

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Title:
The discovery of 3.8 hour periodic intensity dips and eclipses from the transient low-mass X-ray binary EXO 0748-676
Authors:
Parmar, A. N.; White, N. E.; Giommi, P.; Gottwald, M.
Affiliation:
AA(EXOSAT Observatory, Darmstadt, West Germany), AB(EXOSAT Observatory, Darmstadt, West Germany), AC(EXOSAT Observatory, Darmstadt, West Germany), AD(EXOSAT Observatory, Darmstadt, West Germany)
Journal:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 308, Sept. 1, 1986, p. 199-212. (ApJ Homepage)
Publication Date:
09/1986
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ECLIPSING BINARY STARS, PERIODIC VARIATIONS, X RAY BINARIES, ABUNDANCE, ACCRETION DISKS, COMPANION STARS, INTERSTELLAR MATTER, METALLICITY
Bibliographic Code:
1986ApJ...308..199P

Abstract

Exosat observations of EXO 0748-676 obtained at 1-10 keV with the medium-energy proportional-counter array during February-July 1985 are reported and analyzed. The source is found to exhibit X-ray eclipses of duration 8.3 min and period 3.82 h; a main-sequence secondary would have mass 0.45 solar mass, with system inclination 75 deg. Intensity dips of up to 80 percent are observed at orbital phase 0.8-0.2 and attributed to obscuration of the X-ray primary by a thickened region at the outer edge of the accretion disk.

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Title:
New X-ray and optical observations of the X-ray discovered QSO-galaxy pair 1E 0104.2 + 3153
Authors:
Gioia, I. M.; Maccacaro, T.; Schild, R. E.; Giommi, P.; Stocke, J. T.
Affiliation:
AA(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AB(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AC(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AD(EXOSAT Observatory, Darmstadt, West Germany), AE(Colorado, University, Boulder)
Journal:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 307, Aug. 15, 1986, p. 497-503. (ApJ Homepage)
Publication Date:
08/1986
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
GALACTIC RADIATION, QUASARS, VISUAL OBSERVATION, X RAY ASTRONOMY, ABSORPTION SPECTRA, ASTRONOMICAL SPECTROSCOPY, EXOSAT SATELLITE, SPECTRAL LINE WIDTH
Bibliographic Code:
1986ApJ...307..497G

Abstract

New X-ray and optical observations are presented of the QSO-galaxy pair 1E 0104.2 + 3153, originally discovered as a serendipitous source in the Einstein Observatory Medium Sensitivity Survey (Gioia et al., 1984). Results from an extremely deep Exosat observation are used to suggest that the QSO rather than the compact group of galaxies is the optical counterpart of the IPC source. High-resolution (1-A) spectroscopy of the broad-absorption-line QSO, which fails to confirm the Ca II H and K absorption features reported by Stocke et al., (1984), is presented and discussed. The presence of broad absorption lines in the QSO spectrum may indicate that intrinsic absorption is the cause of the nondetection of this source in the soft Exosat energy band. Optical monitoring of the QSO over a 2-yr period indicates variability. Possible interpretations of this phenomenon are intrinsic luminosity variation or a cessation of a gravitational lensing effect acting at the time of the Einstein observation.

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Title:
Rapid X-ray and optical variability in the X-ray selected BL Lacertae object IE 1402.3 + 0416
Authors:
Giommi, Paolo; Barr, Paul; Gioia, Isabella M.; Maccacaro, Tommaso; Schild, Rudolph; Garilli, Bianca; Maccagni, Dario
Affiliation:
AA(EXOSAT Observatory, Darmstadt, West Germany), AB(EXOSAT Observatory, Darmstadt, West Germany), AC(Harvard-Smithsonian Center for Astrophysics, Cambridge), AD(Harvard-Smithsonian Center for Astrophysics, Cambridge), AE(Harvard-Smithsonian Center for Astrophysics, Cambridge)
Journal:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 303, April 15, 1986, p. 596-600. ESA-supported research. (ApJ Homepage)
Publication Date:
04/1986
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
BL LACERTAE OBJECTS, X RAY SOURCES, EMISSION SPECTRA, EXOSAT SATELLITE, HEAO 2, MAGNITUDE, RADIANT FLUX DENSITY, SPECTRAL ENERGY DISTRIBUTION, VARIABILITY, X RAY SPECTRA
Bibliographic Code:
1986ApJ...303..596G

Abstract

Results from X-ray and optical observations of the X-ray-discovered BL Lac object 1E 1402.3 + 0416 are presented, where the X-ray measurements were carried out with the Channel Multiplier Array (CMA) and Medium Energy experiment (ME) detectors on board Exosat. These measurements revealed an intensity decrease by a factor of two on a time scale of a few hours. At maximum flux, the source was significantly greater than at the time of the Einstein Image Proportional Counter (IPC) discovery observation. The 2-6 keV X-ray spectrum was determined by the ME experiment, and IPC, HRI, and CMA data were subsequently compared. The source varied over the years by a factor of five; its brightest state was within the last three years. It is noted that a redshift greater than 0.2 would require that anisotropic emission mechanisms be invoked.

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Title:
X-rays from the magnetic white dwarf PG 1658 + 441
Authors:
Pravdo, S. H.; Marshall, F. E.; White, N. E.; Giommi, P.
Affiliation:
AA(California Institute of Technology, Jet Propulsion Laboratory, Pasadena), AB(NASA, Goddard Space Flight Center, Greenbelt, MD), AC(EXOSAT Observatory, Darmstadt, West Germany), AD(EXOSAT Observatory, Darmstadt, West Germany)
Journal:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 300, Jan. 15, 1986, p. 819-823. NASA-supported research. (ApJ Homepage)
Publication Date:
01/1986
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
MAGNETIC STARS, WHITE DWARF STARS, X RAY SOURCES, X RAY SPECTRA, STELLAR ATMOSPHERES, STELLAR COMPOSITION, STELLAR SPECTRA, STELLAR TEMPERATURE
Bibliographic Code:
1986ApJ...300..819P

Abstract

X-ray emission has been detected from PG 1658 + 441, a hot, isolated, magnetic white dwarf. The source was first detected in an Einstein IPC observation and was later identified in an Exosat channel multiplier array observation. Both imaging observations were motivated by an attempt to find the optical counterpart to the HEAO 1 soft X-ray source H1659 + 44. Spectral analysis, however, indicates that H1659 + 44 and PG 1658 + 441 are unrelated. The broad-band spectrum of this DA white dwarf can be explained as emission from a homogeneous, high-gravity, pure hydrogen atmosphere with a temperature near 28,000 K. The observations of PG 1658 + 441 support the suggestion that a correlation exists between temperature and helium abundance in white dwarf atmospheres.

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Title:
Rapid X-Ray Variability in Active Galactic Nuclei /p/
Authors:
Barr, P.; Mushotzky, R.; Giommi, P.; Clavel, J.; Wamsteker, W.
Journal:
Quasars; Proceedings of the IAU Symposium, Bangalore, India, Dec. 2-6, 1985. Edited by Govind Swarup and V. K. Kapahi. Symposium sponsored by IAU, Tata Institute of Fundamental Research, Department of Science and Technology of India, et al. Dordrecht, D. Reidel Publishing Co. (IAU Symposium, No. 119), 1986., p.269
Publication Date:
00/1986
Origin:
ADS
Bibliographic Code:
1986IAUS..119..269B

Abstract

Not Available

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Title:
X-Ray Selected BL Lac Objects : Time Variability and X-Ray Spectrum /p/
Authors:
Maccagni, D.; Barr, P.; Garilli, B.; Gioia, I. M.; Giommi, P.; Maccacaro, T.; Schild, R.
Journal:
Quasars; Proceedings of the IAU Symposium, Bangalore, India, Dec. 2-6, 1985. Edited by Govind Swarup and V. K. Kapahi. Symposium sponsored by IAU, Tata Institute of Fundamental Research, Department of Science and Technology of India, et al. Dordrecht, D. Reidel Publishing Co. (IAU Symposium, No. 119), 1986., p.265
Publication Date:
00/1986
Origin:
ADS
Bibliographic Code:
1986IAUS..119..265M

Abstract

Not Available

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Title:
A Statistical Study of the Relationship Between X-Ray Optical and Radio Luminosity for a Sample of QSOs /p/
Authors:
Worrall, D. M.; Giommi, P.; Tananbaum, H.; Zamorani, G.
Journal:
Quasars; Proceedings of the IAU Symposium, Bangalore, India, Dec. 2-6, 1985. Edited by Govind Swarup and V. K. Kapahi. Symposium sponsored by IAU, Tata Institute of Fundamental Research, Department of Science and Technology of India, et al. Dordrecht, D. Reidel Publishing Co. (IAU Symposium, No. 119), 1986., p.263
Publication Date:
00/1986
Origin:
ADS
Bibliographic Code:
1986IAUS..119..263W

Abstract

Not Available

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Title:
The identification of H2311 + 77 with HD220140, a probable RS CVn star
Authors:
Pravdo, S. H.; White, N. E.; Giommi, P.
Affiliation:
AA(California Institute of Technology, Jet Propulsion Laboratory, Pasadena), AB(EXOSAT Observatory, Darmstadt, West Germany), AC(EXOSAT Observatory, Darmstadt, West Germany)
Journal:
Royal Astronomical Society, Monthly Notices (ISSN 0035-8711), vol. 215, July 1, 1985, p. 11P-13P. NASA-supported research. (MNRAS Homepage)
Publication Date:
07/1985
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
BINARY STARS, LATE STARS, X RAY SOURCES, EXOSAT SATELLITE, HEAO 1, MAIN SEQUENCE STARS, STELLAR LUMINOSITY, STELLAR ROTATION
Bibliographic Code:
1985MNRAS.215P..11P

Abstract

H2311 + 77, one of the bright soft X-ray sources in the sky originally detected with HEAO 1, has been identified in an Exosat imaging observation with a 7.7-mag late-type star, HD220140. The X-ray luminosity and the optical characteristics of this star indicate that it is probably an RS CVn binary system.

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Title:
The EXO 0748-676: an exciting new X-ray transient
Authors:
Parmar, A. N.; Gottwald, M.; Haberl, F.; Giommi, P.; White, N. E.
Affiliation:
European Space Agency. European Space Operations Center, Darmstadt (Germany).
Journal:
In ESA Recent Results on Cataclysmic Variables p 119-122 (SEE N86-20287 10-93)
Publication Date:
06/1985
Category:
Space Radiation
Origin:
STI
NASA/STI Keywords:
ECLIPSING BINARY STARS, EXOSAT SATELLITE, STELLAR RADIATION, X RAY SOURCES, ACCRETION DISKS, LIGHT CURVE, PERIODIC VARIATIONS, STELLAR SPECTRA
Bibliographic Code:
1985cava.rept..119P

Abstract

The results of EXOSAT observations of the X-ray transient EXO 0748-676 are presented. This source shows X-ray eclipses, irregular intensity dips, and X-ray bursts. The eclipses last for 8.3 min and recur with a period of 3.8 hr. The intensity dips occur between phases 0.5 and 0.1 (where center of eclipse is 0.0) and are associated with an increase in low energy absorption. As the intensity of EXO 0748-676 decayed by a factor 2 over an interval of 50 days the shape of the 2 to 10 keV light curve changed such that the dips were centered on phase 0.0. In addition to 18 single type 1 bursts, 3 double X-ray bursts are observed. The luminosity of the second burst in a pair is 0.3 of the first. The rise and decay times of the second bursts appear to be more rapid than the first bursts.

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Title:
EXOSAT observation of the QSO galaxy pair 1E0104.2+3153
Authors:
Giommi, P.; Gioia, I. M.; Maccacaro, T.
Affiliation:
AA(EXOSAT Observatory, Darmstadt, West Germany), AB(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AC(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA)
Journal:
(ESA, ESLAB Symposium on X-Ray Astronomy in the EXOSAT Era, 18th, The Hague, Netherlands, Nov. 5-9, 1984) Space Science Reviews (ISSN 0038-6308), vol. 40, April 1985, p. 627-631. (SSRv Homepage)
Publication Date:
04/1985
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
CHANNEL MULTIPLIERS, ELLIPTICAL GALAXIES, GRAVITATIONAL LENSES, QUASARS, X RAY SOURCES, BREMSSTRAHLUNG, EXOSAT SATELLITE, OBSERVATION
Bibliographic Code:
1985SSRv...40..627G

Abstract

A very long (160,000 second) observation of the X-ray source 1E0104.2+3153 was carried out using the Channel Multiplier Array (CMA) instrument on board Exosat in August 17, 1984. A thin Lexan filter having maximum throughput in the 0.05-2.0 keV CMA band was used during the entire observation period. The positional accuracy of the CMA was sufficient to distinguish between the different optical counterparts of the source. The IPC flux and the CMA 3 sigma upper limit are plotted in a graph as a function of temperature (in the case of a thermal bremsstrahlung spectrum), and of photon spectral index (in the case of a power law spectrum). Significant variation in the X-ray luminosity of 1E0104.2+3153 was observed. Some possible reasons for the variability are discussed.

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Title:
EXO 1747-214
Authors:
Parmar, A. N.; White, N. E.; Giommi, P.; Stella, L.; Sweeney, M.; Watson, M.
Journal:
IAU Circ., 4058, 2 (1985). Edited by Marsden, B. G. (IAUC Homepage)
Publication Date:
04/1985
Origin:
CBAT
Objects:
EXO 1747-214
Bibliographic Code:
1985IAUC.4058....2P

Abstract

IAUC 4058 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
X-ray and Optical Observations of Four X-ray Selected BL Lac Objects
Authors:
Giommi, P.; Barr, P.; Maccagni, D.; Garilli, B.; Gioia, I. M.; Maccacaro, T.; Schild, R.; Stocke, J.
Journal:
Bulletin of the American Astronomical Society, Vol. 17, p.608
Publication Date:
03/1985
Origin:
ADS
Bibliographic Code:
1985BAAS...17..608G

Abstract

Not Available

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Title:
Rapid X-ray Variability in NGC 3031 (M81)
Authors:
Barr, P.; Giommi, P.; Wamsteker, W.; Gilmozzi, R.; Mushotzky, R. F.
Journal:
Bulletin of the American Astronomical Society, Vol. 17, p.608
Publication Date:
03/1985
Origin:
ADS
Bibliographic Code:
1985BAAS...17..608B

Abstract

Not Available

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Title:
EXOSAT Observations of the Transient EXO 0748-676
Authors:
Gottwald, M.; Parmar, A.; Giommi, P.; Haberl, F.; White, N. E.
Journal:
Bulletin of the American Astronomical Society, Vol. 17, p.590
Publication Date:
03/1985
Origin:
ADS
Bibliographic Code:
1985BAAS...17..590G

Abstract

Not Available

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Title:
NGC 3031
Authors:
Barr, P.; Giommi, P.
Journal:
IAU Circ., 4044, 2 (1985). Edited by Marsden, B. G. (IAUC Homepage)
Publication Date:
03/1985
Origin:
CBAT
Objects:
NGC 3031
Bibliographic Code:
1985IAUC.4044....2B

Abstract

IAUC 4044 available courtesy of the Central Bureau for Astronomical Telegrams. IAUC 4044 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
The discovery of a 25 min regular modulation in the X-ray flux from 2S0142 + 61
Authors:
White, N. E.; Giommi, P.; Parmar, A. N.; Marshall, F. E.; Mason, K. O.
Affiliation:
AA(EXOSAT Observatory, Darmstadt, West Germany), AB(EXOSAT Observatory, Darmstadt, West Germany), AC(EXOSAT Observatory, Darmstadt, West Germany), AD(NASA, Goddard Space Flight Center, Greenbelt, MD), AE(London, University College, Dorking, England)
Journal:
(ESA, ESLAB Symposium on X-Ray Astronomy in the EXOSAT Era, 18th, The Hague, Netherlands, Nov. 5-9, 1984) Space Science Reviews (ISSN 0038-6308), vol. 40, Feb. 1985, p. 157-162. (SSRv Homepage)
Publication Date:
02/1985
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ASTRONOMICAL SPECTROSCOPY, PERIODIC VARIATIONS, RADIANT FLUX DENSITY, SPACEBORNE ASTRONOMY, X RAY SOURCES, EXOSAT SATELLITE, LIGHT CURVE, MODULATION, SPECTRAL ENERGY DISTRIBUTION, STELLAR SPECTROPHOTOMETRY
Bibliographic Code:
1985SSRv...40..157W

Abstract

A 13 hr observation of 2S0142 + 61 on August 27, 1984 by EXOSAT shows the X-ray flux of 2S0142 + 61 to be modulated with a period of 1456+/-6 s. The 1-10 keV spectrum is two component with an approximately 0.7 keV thermal and 0.0 energy index power law, with 30 percent of the total luminosity in the thermal component. The spectrum is absorbed by about 1 x 10 to the 22nd H per sq cm. Only the hard component is pulsed with a 3 to 10 keV peak to mean amplitude of 35 percent. Below 2 keV the modulation is less than a few percent. The total 1-10 keV luminosity is 3.5 x 10 to the 32nd erg/s for a distance of 100 pc. Possible optical counterparts are discussed.

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Title:
EXO 0748-676
Authors:
Parmar, A. N.; White, N. E.; Giommi, P.; Haberl, F.; Pedersen, H.; Mayor, M.
Journal:
IAU Circ., 4039, 1 (1985). Edited by Marsden, B. G. (IAUC Homepage)
Publication Date:
02/1985
Origin:
CBAT
Objects:
EXO 0748-676
Bibliographic Code:
1985IAUC.4039....1P

Abstract

IAUC 4039 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
E 1402.3+0416
Authors:
Giommi, P.; Barr, P.
Journal:
IAU Circ., 4033, 3 (1985). Edited by Marsden, B. G. (IAUC Homepage)
Publication Date:
02/1985
Origin:
CBAT
Objects:
1E 1402.3+0416
Bibliographic Code:
1985IAUC.4033....3G

Abstract

IAUC 4033 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
EXO:0748-676 - an Exciting New X-Ray Transient
Authors:
Parmar, A. N.; Gottwald, M.; Haberl, F.; Giommi, P.; White, N. E.
Journal:
Recent Results on Cataclysmic Variables. The Importance of IUE and Exosat Results on Cataclysmic Variables and Low-Mass X-Ray Binaries. Proceedings of an ESA workshop held at Remeis Observatory, Bamberg, Germany, April 17-19, 1985. Editor, European Space Agency, Paris, France; Publishers, ESA Scientific andTechnical Publications Branch, Noordwijk, Netherlands, 1985. ISSN # 0379-6566. LC # QB821 .R43 1985, P.119, 1985
Publication Date:
00/1985
Origin:
ADS
Bibliographic Code:
1985rrcv.work..119P

Abstract

Not Available

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Title:
S 0142+61
Authors:
White, N. E.; Giommi, P.; Parmar, A. N.; Marshall, F. E.
Journal:
IAU Circ., 3996, 2 (1984). Edited by Marsden, B. G. (IAUC Homepage)
Publication Date:
10/1984
Origin:
CBAT
Objects:
2S 0142+61
Bibliographic Code:
1984IAUC.3996....2W

Abstract

IAUC 3996 available courtesy of the Central Bureau for Astronomical Telegrams.

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Title:
New Observations of the X-ray Discovered QSO-Galaxy Pair 1E0104.2+3153
Authors:
Gioia, I. M.; Maccacaro, T.; Schild, R.; Giommi, P.; Stocke, J.
Journal:
Bulletin of the American Astronomical Society, Vol. 16, p.932
Publication Date:
09/1984
Origin:
ADS
Bibliographic Code:
1984BAAS...16..932G

Abstract

Not Available

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Title:
EXOSAT observation of the candidate X-ray counterpart of Geminga
Authors:
Caraveo, P. A.; Bignami, G. F.; Giommi, P.; Mereghetti, S.; Paul, J. A.
Affiliation:
AA(CNR, Istituto di Fisica Cosmica, Milan, Italy), AB(CNR, Istituto di Fisica Cosmica, Milan, Italy), AC(Exosat Observatory, Darmstadt, West Germany), AD(Milano, Universita, Milan, Italy), AE(Commissariat a l'Energie Atomique, Centre d'Etudes Nucleaires de Saclay, Gif-sur-Yvette, Essonne, France)
Journal:
Nature (ISSN 0028-0836), vol. 310, Aug. 9, 1984, p. 481-483.
Publication Date:
08/1984
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
EXOSAT SATELLITE, GAMMA RAY ASTRONOMY, X RAY SOURCES, CHANNEL MULTIPLIERS, TIME MEASUREMENT, VARIABLE STARS
Bibliographic Code:
1984Natur.310..481C

Abstract

The Einstein Observatory has uncovered a new X-ray source, 1E0630 + 178, within the about 0.5 sq deg error box of the gamma-ray source 'Geminga' (2GC195 + 4). On the basis of the properties noted, this object has been proposed as Geminga's X-ray counterpart. A faint, star-like object lying at the inner boundary of the HRI 98-percent error box has been suggested as the optical counterpart of the X-ray/gamma-ray source. Several searches have failed to detect a radio counterpart.

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Title:
X-ray variability of quasars
Authors:
Zamorani, G.; Maccacaro, T.; Giommi, P.; Tananbaum, H.
Affiliation:
AA(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA; CNR, Istituto di Radioastronomia, Bologna, Italy), AB(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA; CNR, Istituto di Radioastronomia, Bologna, Italy), AC(EXOSAT Observatory, Darmstadt, West Germany), AD(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA)
Journal:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 278, March 1, 1984, p. 28-36. Research supported by the Consiglio Nazionale delle Ricerche. (ApJ Homepage)
Publication Date:
03/1984
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
QUASARS, X RAY SOURCES, HEAO 2, STATISTICAL ANALYSIS, VARIABILITY
Bibliographic Code:
1984ApJ...278...28Z

Abstract

Fifty-one previously known quasars observed with the Einstein Observatory have been analyzed for intensity variations on time scales ranging from a few hundred seconds to 18 months. While none of them has shown variability on a very short time scale, four of the quasars have been seen to vary on a time scale of about 1 day. As about 30 objects could be analyzed on this time scale, it is concluded that 1 day appears to be a relatively common time scale for variability. On longer time scales (6-18 months), nine out of 12 quasars which could be analyzed show variability. However, in contrast to results previously reported for BL Lac objects, no variation in quasar luminosity larger than a factor of 2 has been observed.

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Title:
EXOSAT Observations of Geminga (==1E0630.9+1748=2CG 195+04)
Authors:
Caraveo, P. A.; Bignami, G. F.; Giommi, P.
Journal:
Bulletin of the American Astronomical Society, Vol. 15, p.908
Publication Date:
09/1983
Origin:
ADS
Bibliographic Code:
1983BAAS...15R.908C

Abstract

Not Available

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Title:
X-Ray Variability of Quasars
Authors:
Zamorani, G.; Giommi, P.; Maccacaro, T.; Tananbaum, H.
Journal:
QUASARS & GRAVITATIONAL LENSES: 24TH LIEGE 83JUN P.451, 1983
Publication Date:
06/1983
Origin:
KNUDSEN
Bibliographic Code:
1983qgl..conf..451Z

Abstract

Not Available

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Title:
The cosmological evolution and luminosity function of X-ray selected active galactic nuclei
Authors:
Maccacaro, T.; Gioia, I. M.; Avni, Y.; Giommi, P.; Griffiths, R. E.; Liebert, J.; Stocke, J.; Danziger, J.
Affiliation:
AA(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA; CNR, Istituto di Radioastronomia, Bologna, Italy), AB(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA; CNR, Istituto di Radioastronomia, Bologna, Italy), AC(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA; Weizmann Institute of Science, Rehovot, Israel), AD(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AE(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AF(Steward Observatory, Tucson, AZ), AG(Steward Observatory, Tucson, AZ), AH(European Southern Observatory, Munich, West Germany)
Journal:
Astrophysical Journal, Part 2 - Letters to the Editor, vol. 266, Mar. 15, 1983, p. L73-L77. Research supported by the Servizio Attivita Spaziali; (ApJ Homepage)
Publication Date:
03/1983
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ACTIVE GALACTIC NUCLEI, COSMOLOGY, GALACTIC EVOLUTION, LUMINOSITY, QUASARS, X RAY SOURCES, FUNCTIONS (MATHEMATICS), SPATIAL DISTRIBUTION
Bibliographic Code:
1983ApJ...266L..73M

Abstract

The cosmological evolution and the X-ray luminosity function of X-ray selected active galactic nuclei (AGNs) are derived and discussed. The sample used consists of 31 AGNs extracted from a fully identified sample of X-ray sources from the Einstein Observatory Medium Sensitivity Survey and is therefore exclusively defined by its X-ray properties. The distribution in space is found to be strongly nonuniform. The amount of cosmological evolution required by the X-ray data is derived in the framework of pure luminosity evolution and is found to be smaller than the amount determined from optically selected samples. The X-ray luminosity function is derived. It can be satisfactorily represented by a single power law only over a limited range of absolute luminosities. Evidence that the luminosity function flattens at low luminosity or steepens at high luminosity, or both, is presented and discussed.

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Title:
Discovery of a new BL Lacertae object /1E 1402.3 + 0416/ with the Einstein Observatory
Authors:
Stocke, J.; Liebert, J.; Stockman, H.; Danziger, J.; Lub, J.; Maccacaro, T.; Griffiths, R.; Giommi, P.
Affiliation:
AA(Stewart Observatory, Tucson, AZ), AB(Stewart Observatory, Tucson, AZ), AC(Stewart Observatory, Tucson, AZ), AD(European Southern Observatory, Munich, West Germany), AE(European Southern Observatory, Munich, West Germany), AF(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA; CNR, Istituto di Radioastronomia, Bologna, Italy), AG(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AH(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA)
Journal:
Royal Astronomical Society, Monthly Notices, vol. 200, July 1982, p. 27P-32P. NSF No. AST-78-22714; (MNRAS Homepage)
Publication Date:
07/1982
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
BL LACERTAE OBJECTS, BLUE STARS, HEAO 2, X RAY SOURCES, ACTIVE GALAXIES, BACKGROUND RADIATION, GALACTIC NUCLEI, QUASARS, RADIANT FLUX DENSITY, SEYFERT GALAXIES, SPECTROPHOTOMETRY, STELLAR EVOLUTION
Bibliographic Code:
1982MNRAS.200P..27S

Abstract

It is noted that only one BL Lac object, designated 1E 1402.3 + 0416, has so far been discovered as part of an optical identification program for a complete sample of faint X-ray sources detected with the Einstein Observatory. Consistent with previously X-ray-discovered BL Lacs, this object is blue and radio weak (17 mJy at 6 cm). It is pointed out that the percentage of BL Lacs in the faint extragalactic X-ray sample (2%) is smaller than the percentage at higher X-ray fluxes (6%). Over the same range in X-ray flux, the percentage of emission-line active galaxy nuclei (QSO + Seyferts) rises from 40% to 74%). This is seen as suggesting that BL Lacs do not evolve in a manner similar to quasars and are, therefore, not substantial contributors to the X-ray background.

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Title:
On the Space Density of BL Lac Objects
Authors:
Maccacaro, T.; Danziger, J.; Giommi, P.; Griffiths, R. E.; Liebert, J.; Lub, J.; Stocke, J.; Stockman, H.
Journal:
Bulletin of the American Astronomical Society, Vol. 14, p.650
Publication Date:
03/1982
Origin:
ADS
Bibliographic Code:
1982BAAS...14..650M

Abstract

Not Available

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Title:
On the Redshift and Luminosity Distribution of X-ray Selected QSOs
Authors:
Giommi, P.; Avni, Y.; Gioia, I. M.; Maccacaro, T.; Stocke, J.; Zamorant, G.
Journal:
Bulletin of the American Astronomical Society, Vol. 14, p.632
Publication Date:
03/1982
Origin:
ADS
Bibliographic Code:
1982BAAS...14..632G

Abstract

Not Available

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Title:
The Fluctuations of the Cosmic X-Ray Background as a Sensitive Tool to the Universal Source Distribution
Authors:
Giommi, P.; Bignami, G. F.
Journal:
ORIGIN OF COSMIC RAYS - IAU SYMP.94, BOLOGNA 1981 P.277, 1981
Publication Date:
00/1981
Origin:
KNUDSEN
Bibliographic Code:
1981IAUS...94..277G

Abstract

Not Available

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