GRB 050813: Possible Short Swift-BAT GRB

TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 3788
SUBJECT: GRB 050813: Possible Short Swift-BAT GRB
DATE: 05/08/13 08:06:42 GMT
FROM: Craig Markwardt at NASA/GSFC/UMD craigm@milkyway.gsfc.nasa.gov

A. Retter (PSU), L. Barbier (GSFC), S. Barthelmy (GSFC), A. Blustin (MSSL), D. Burrows (PSU), A. Cucchiara (PSU), N. Gehrels (GSFC), O. Godet (U. Leicester), J. Kennea (PSU), C. Markwardt (GSFC/UMD), D. Morris (PSU), D. Palmer (LANL), J. Racusin (PSU), P. Roming (PSU) on behalf of the Swift team, report:

At 06:45:09.8 UT, Swift-BAT triggered and located GRB050813 (trigger=150139). The spacecraft slewed immediately. The BAT on-board calculated location is RA,Dec 242.010, +11.252 {+16h 08m 02s, +11d 15′ 07″} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). There is a single peak with an approximate duration of 0.7 sec FWHM. The peak rate is approx 2000 ct/s in the 15-350 keV band.

At 06:46:23 UT XRT attempted to centroid on the BAT position, 73 secs after the BAT trigger. No position was acquired by the onboard software and the TDRSS lightcurve shows no evidence for a decaying x-ray source. We can not rule out the presence of a weak x-ray source like that seen for the early afterglow of short GRB 050509b. We await ground analysis of the early XRT data following the first Malindi pass.

The UVOT began observing this trigger at 06:46:52.0 UT, 102 seconds after the BAT trigger. No new source (compared to the DSS image) is observed in the 100 second V-band UVOT GeNI image down to a 5-sigma upper limit of 18.15 mag.

This trigger (=150139) appears to be a real GRB, as opposed to the recently retracted trigger (=150131).