TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  409
SUBJECT: GRB990907: BeppoSAX follow up and X-ray afterglow
DATE:    99/09/15 17:48:07 GMT
FROM:    Luigi Piro at IAS/CNR Frascati  <piro@alpha1.ias.rm.cnr.it>

L. Piro (IAS/CNR), M. Capalbi, R. Ricci (BeppoSAX SDC), M. Dadina
(IAS/CNR & BeppoSAX SOC), L. Di Ciolo (BeppoSAX SOC), C. De Libero
(BeppoSAX OCC), R.C. Butler (ASI)  report:
 
A BeppoSAX follow-up observation of GRB990907 (GCN 405)
started on Sept. 8, 4:32 U.T.  Due to technical problems the observation
lasted 20 minutes only, with an exposure time of 1070 s. in the
MECS(1.6-10 keV).  A previously unknown X-ray source 1SAXJ0731.2-6928
is detected within the WFC error box with  a MECS count rate of
(2.0+/-0.6)x10^-2 cts/s.
The position (equinox 2000) is R.A.=7h 31m 12 s Decl=-69 28' 10", i.e.
4' away from the center of the WFC position (GCN405).
Due to the vicinity of the source to the support grid of the detector
we estimate an error of 3' in radius and a flux (2-10 keV) between 1 and
2 x 10^-12 erg/cm^2/s.  The probability that a serendipitous source
with similar strength is found in the WFC error circle is about 3x10^-3.
We conclude that 1SAXJ0731.2-6928 is likely the X-ray afterglow of GRB990907.