GRB 050712: Swift detection of a weak burst

TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 3573
SUBJECT: GRB 050712: Swift detection of a weak burst
DATE: 05/07/12 15:04:45 GMT
FROM: David Burrows at PSU/Swift dxb15@psu.edu

D. Grupe (PSU), S. Barthelmy (GSFC), J. Cummings, (GSFC/NRC), H. Krimm (GSFC/USRA), C. Markwardt, (GSFC/UMD), D. Palmer (LANL), T. Sakamoto (GSFC), D. Burrows, J. Nousek, A. Falcone, C. Gronwall (PSU), T. Poole, A. Blustin (MSSL), and N. Gehrels (GSFC) on behalf of the Swift team:

At 14:00:27.51 UT, the Swift Burst Alert Telescope (BAT) triggered and located on-board GRB050712 (trigger=145581). The spacecraft slewed immediately. The flight-determined location is RA,Dec 77.693,+64.899 {+05h 10m 46s,+64d 53′ 56″} (J2000) with an uncertainty of 3 arcmin (radius, stat+sys). The burst lightcurve has 4-5 peaks all within ~35 sec duration. This is a weak burst with a peak count rate of 500 cnts/sec in the 15-350 keV band.

This burst should not be confused with Trigger=145563 two hours earlier today. Based on preliminary analysis, the BAT team believes the earlier trigger is not a real GRB.

The XRT attempted to centroid on the afterglow at 14:03:14 UT (166 s after the BAT trigger) but could not find a bright enough source for a successful on-board centroid. Ground analysis will be required to determine whether there is an X-ray counterpart.

The Swift Ultra Violet/Optical (UVOT) observations began at 14:03:11.5 UT, 164 seconds after the BAT trigger. The first data taken after the spacecraft settled was a 100 sec exposure using the V filter with the midpoint of the observation at 214 sec after the BAT trigger. Based on comparisons to the DSS, we detect no new source. The 5-sigma upper limit in the V-filter is 17.94 mag.