GRB050815: Swift-BAT detection of a burst

TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 3811
SUBJECT: GRB050815: Swift-BAT detection of a burst
DATE: 05/08/15 18:13:31 GMT
FROM: Derek Fox at CIT derekfox@astro.caltech.edu

D. Fox (PSU), L. Barbier (GSFC), S. Barthelmy (GSFC), D. Burrows (PSU), J. Cummings (GSFC/NRC), N. Gehrels (GSFC), O. Godet (U. Leceister), S.T. Holland (GSFC/USRA), S. Hunsberger (PSU), J. Kennea (PSU), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), F. Marshall (GSFC), D. Morris (PSU), D. Palmer (LANL), K. Page (U. Leicester), A. Parsons (GSFC), P. Roming (PSU), T. Sakamoto (GSFC), P. Schady (PSU/UCL-MSSL), & E. Rol (Leceister) report on behalf of the Swift team:

At 17:25:19 UT, Swift-BAT triggered and located GRB050815 (trigger=150532). The BAT on-board calculated location is RA,Dec 293.575d,+9.166d {19h 34m 18s,+09d 09′ 59″}, with an uncertainty of 2 arcmin (radius, 90% containment, stat+sys). The BAT light curve shows two peaks in 5 sec and possible low energy emission out to ~30 sec. The peak count rate was ~1000 counts/sec (15-350 keV), at ~2 seconds after the trigger.

The S/C slewed immediately and the XRT began taking data at 17:26:28, 70 s after the BAT trigger. The XRT on-board centroid algorithm did not converge and no prompt position is available. However, the XRT lightcurve shows evidence of a decaying source in the field of view. We are waiting for down-linked data to determine a position.

The UVOT began observing the position of trigger #150532 at 17:26:25.5 UT, 67 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 ~ 1.6 magnitudes. The UVOT image gives 55% coverage of the BAT error circle. The BAT source is located in a crowded star field.