GRB050819: Swift-BAT detection of a weak burst
TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 3826
SUBJECT: GRB050819: Swift-BAT detection of a weak burst
DATE: 05/08/19 17:23:53 GMT
FROM: Scott Barthelmy at NASA/GSFC Scott@lheamail.gsfc.nasa.gov
M. De Pasquale (MSSL), S. Barthelmy (GSFC), A.P. Beardmore (U Leicester), D. Burrows (PSU), M. Chester (PSU), A. Cucchiara (PSU), J. Cummings (GSFC/NRC), N. Gehrels (GSFC), M.R. Goad (U Leicester), J. Kennea (PSU), H. Krimm (GSFC/USRA), S.T. Holland (GSFC/USRA), S. Hunsberger (PSU), F. Marshall (GSFC), C. Markwardt (GSFC/UMD), J.P. Osborne (U Leicester), K.L. Page (U Leicester), D. Palmer (LANL), A. Parsons (GSFC), P. Roming (PSU), T. Sakamoto (GSFC), M. Still (GSFC) on behalf of the Swift team:
At 16:23:55 UT, Swift-BAT triggered and located GRB050819 (trigger 151131). The BAT on-board calculated location is RA,Dec 358.735d,+24.854d {23h 54m 56s,+24d 51′ 13″} (J2000), with an uncertainty of 2 arcmin (radius, 90% containment, stat+sys). The BAT light curve shows a very broad shallow peak of about 40 seconds duration. The peak count rate was ~400 counts/sec (15-350 keV) at ~10 seconds after the trigger.
The spacecraft slewed immediately and the XRT began taking data at 16:26:15.8, 141 seconds after the BAT trigger. There were not enough counts in the first 2.5 s image for a successful on-board centroid. However, the light-curve shows evidence for a decaying X-ray source in the field of view and the spectrum appears consistent with that of a GRB.
The UVOT began observing the position of the trigger at 16:26:13.5 UT, 138 s after the BAT trigger. In a 100 s V-band image, no new source is detected with respect to the DSS down to a 5 sigma upper limit of 18.1 mag. The estimated extinction in this direction is A_V ~ 0.4 magnitudes. The UVOT image gives 50% coverage assuming a BAT error circle of 2 arcmin radius.
