TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3320
SUBJECT: Swift/BAT possible detection of a weak burst GRB050430
DATE:    05/04/30 14:47:17 GMT
FROM:    Bing Zhang at U Nevada,Las Vegas  <bzhang@physics.unlv.edu>

B. Zhang (UNLV), D. Palmer (LANL), S. Barthelmy (GSFC), A. Falcone
(PSU), D. Burrows (PSU), M. Chester (PSU),
J. Kennea (PSU), C. Pagani (PSU), N. Gehrels (GSFC)

on behalf of the Swift Team.

At 13:29:35 UT, the Swift Burst Alert Telescope (BAT) triggered
and located GRB050430 (trigger #115881).  The BAT on-board
calculated location is RA, Dec 328.684,+47.795 (J2000) with an
uncertainty of 4 arcmin (radius, 3-sigma, including estimated
systematic uncertainty).  The BAT light curve has 4 or 5 small,
near-threshold peaks (800 cnts/sec, 15-350 keV) with a total
duration of 25 (possible 55) sec.  This burst occurred while
entering the SAA, and given the weakness of this trigger, the
validity of this burst is a little in doubt.  Also, a problem
with the intranet inside building 2 at GSFC is limiting the
analysis on this trigger, and therefore the veracity of the
conclusion.

The spacecraft executed a prompt slew and the XRT began observations
of the BAT position at 13:31:59.2 UT.  The XRT sent out a centroid
position through TDRSS, but the Postage Stamp image shows that the
object in this image is a cosmic ray, not an X-ray source.  This
strongly suggests that there was no bright X-ray source in the XRT
field of view, raising the possibility that the trigger may not be a
real GRB.  Updated analysis results based on ground analysis of the
full data set will follow.  We emphasize that the XRT Position sent
out in the GCN Notice is INCORRECT.  Any ground-based searches should
be based on the BAT position until an updated XRT position is
available.

The Swift Ultra-Violet/Optical Telescope (UVOT) began observations at
about 13:32 UT.  Information on UVOT observations will be published in
a subsequent GCN Circular.