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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 I