GRB 050915: Swift detection of a GRB

TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 3977
SUBJECT: GRB 050915: Swift detection of a GRB
DATE: 05/09/15 12:07:39 GMT
FROM: David Palmer at LANL dmpalmer@mac.com

D. Grupe (PSU), A. Beardmore (U. Leicester), D. Burrows (PSU), J. Cummings (GSFC/NRC), K. Page (U. Leicester), D. Palmer (LANL), P. Roming (PSU), E. Rol (U. Leicester) N. Gehrels (GSFC) on behalf of the Swift Team

At 11:22:42 UT, Swift-BAT triggered and located GRB050915 (trigger=155242). The BAT on-board calculated location is RA,Dec 81.714d, -28.030d {05h 26m 51s, -28d 01′ 48″} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). The BAT light curve showed a multi-peak structure with at least 4 well-separated peaks and a total duration of 25 sec. The peak count rate was ~1500 counts/sec (15-350 keV), at ~14 seconds after the trigger.

The spacecraft slewed immediately and the XRT began observing the BAT position at 11:24:09 UT (T+87 s). The count rate was too low for an on-board centroid, but the spectrum and lightcurve strongly suggest that XRT observed a rapidly-fading X-ray source in the field. The XRT position will be available following the next ground station data dump.

UVOT finds no obvious new sources in the BAT error circle in a 100 sec image starting at T+85 s. Further analysis will follow.