BeppoSAX follow-up observations
of the region of the Gamma-ray burst
GRB 970402

The gamma ray burst, GRB 970402, was discovered simultaneously in the data from the Gamma Ray Burst Monitor and Wide Field Cameras onboard by the team of italian/dutch scientists at 10:32 pm on 02 April 1997 who continually monitor the satellite data at the Scientific Operations Center in Nuova Telespazio, Rome.
On the basis of experience gained in the previous observations of such objects , the BeppoSAX Team was able to reschedule the satellite observations and point the BeppoSAX narrow field X-ray telescopes in only 7.5 hours at the gamma-ray burst source. In consequence an X-ray source never before seen was discovered and localized with an accuracy of one hundreth of a degree. The source is actually in the constellation of Octans in the south sky.
A second follow-up has been performed with narrow field instruments after about 1 day. This second observation has shown that the source disappeared. The pictures taken during the two follow-up observations are shown in the figure below.The first one is relatively to MECS observations, the second one to LECS observations.

These data are property of BeppoSAX Team. Any use of these must be authorized by the owners.

These data are property of BeppoSAX Team. Any use of these must be authorized by the owners.

The the two sources in the field are both new X-ray sources

A - 1SAX J1450.1-6920
B - 1SAX J1448.2-6920

Source A is associated with the Gamma Ray Burst GRB 970402 IAUC 6610.
Source B is a serendipitous source with a X-ray flux of the order of 0.01 mCrab.

SAX J0501.7+1146, has been detected by the MECS and LECS at the same position (R.A. = 14h50m6s, Decl. = -69o20'.0, equinox 2000.0; estimated error radius 50"). This position lies at the center of the reported BeppoSAX WFC error box (IAUC 6610) . The source count rate was (3.0+/-0.7)x10E-3 cts sE-1, corresponding to a flux of (1.5 +/- 0.5) x 10E-13 erg cmE-2 sE-1 in the MECS (2-10 keV) and (2.0+/-0.6)x10E-3 cts sE-1 in the LECS (0.5-5 keV) corresponding to (2.0+/-0.6) x 10E-13 erg cmE-2 sE-1 in the 0.5-5 keV range. The flux conversion has been derived assuming the galactic column density and a power law with photon index = 2. The source showed a decreasing trend during the observation. The field was observed again on Apr. 4.634 for 50~000 s. No source was detected in the position of SAX J1450.1-6920. The 3 sigma upper limit on the source flux implies a decrease by a factor of 3 or more.

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