[vsnet-grb-info 1927] Swift-BAT trigger 149118 is probably not a GRB

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3766
SUBJECT: Swift-BAT trigger 149118 is probably not a GRB
DATE:    05/08/05 19:19:17 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <Scott at lheamail.gsfc.nasa.gov>

J. Cummings (GSFC-NRC), S. Barthelmy (GSFC), D. Burrows (PSU),
M. Chester (PSU), N. Gehrels (GSFC), M Goad (U. Leicester),
O. Godet (U. Leicester), J. Kennea (PSU), A. Morgan (PSU),
C. Pagani (PSU), D. Palmer (LANL)
on behalf of the Swift team:

The Swift-BAT trigger (trigger=149118) at 18:04:00 UT on 05 Aug 2005
is not likely to be due to a GRB.  Although we detect an unknown source
in the BAT FOV at RA,Dec=331.154,+29.902 (J2000, 3 arcmin, radius, 90%,
sys+stat), we can not confirm that it is a GRB.  And given that we have
just come out of the gap in the data downlink passes and that there was
a prior backlog of data to download, we will not have access to the
full data set on this trigger for about 8 hours.

At 18:06:00 UT XRT attempted to centroid on the BAT position, 120 secs 
after the BAT trigger.  While the initial TRDSS lightcurve shows
a marginal spike in the count rate, the instrument drops immediately into 
Photon-Counting mode with a very low count rate for the next 100 sec.
Because of the low count rate, no position was acquired by the
on-board software.  We await ground analysis of the early XRT data
following the first Malindi pass.