GRB 051117B: Swift detection of a burst

TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 4281
SUBJECT: GRB 051117B: Swift detection of a burst
DATE: 05/11/17 13:59:44 GMT
FROM: Scott Barthelmy at NASA/GSFC Scott@lheamail.gsfc.nasa.gov

D. Band (PSU), S. Barthelmy (GSFC), A. Beardmore (U Leicester), D. Burrows (PSU), J. Cummings (GSFC/NRC), S.T. Holland (GSFC/USRA), M. Goad (U. Leicester), O. Godet (U. Leicester), N. Gehrels (GSFC), C. Gronwall (PSU), J. Kennea (PSU), H. Krimm (GSFC/USRA), J. Osborne (U Leicester), K. Page (U Leicester) on behalf of the Swift team:

At 13:22:54 UT, Swift-BAT triggered and located GRB 051117B (trigger=164279). The BAT on-board calculated location is RA,Dec 85.225d,-19.245d {05h 40m 54s,-19d 14′ 41″} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). The BAT light curve shows a multi-peak structure with a total duration of ~25 sec. The peak count rate was ~800 counts/sec (15-350 keV), at ~2 seconds after the trigger.

The spacecraft slewed immediately and the XRT began observing the GRB at 13:25:09 UT, 135 sec after the BAT trigger. The on-board detection algorithm did not centroid on a source due to insufficient counts, so no prompt X-ray position is available. However, the XRT prompt light curve and raw spectrum look like a faint GRB. More information will be available around 16:30 UT, after the next Malindi ground-station pass.

UVOT took a finding chart exposure of 200 sec with the V filter starting 133 sec after the BAT trigger. No afterglow candidate has been found in the initial data products. The sub-image covers 19% of the BAT error circle. No afterglow candidate is found in the list of sources generated on-board, which covers 89% of the BAT error circle. The list of sources is typically complete to about 17th mag. No correction has been made for the expected visual extinction of about 0.19 magnitudes.