GRB 050820: Swift detection of a GRB

TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 3830
SUBJECT: GRB 050820: Swift detection of a GRB
DATE: 05/08/20 07:29:30 GMT
FROM: David Burrows at PSU/Swift dxb15@psu.edu

M. Page (UCL-MSSL), D. Burrows (PSU), A. Beardmore (U. Leicester), D. Palmer (LANL), J, Kennea (PSU), N. Gehrels (GSFC), C. Markwardt (GSFC/UMD), K. Page (U. Leicester), T. Sakamoto (GSFC/NRC), M. Chester (PSU), P. Boyd (GSFC) report on behalf of the Swift team:

At 06:34:53 BAT triggered, located, and immediately slewed to GRB 050820 (trigger=151207). The BAT on-board calculated position is RA,Dec 337.400d, +19.578d {22h 29m 36s, 19d 34′ 42″} (J2000) with an uncertainty of 2 arcmin (radius, 90% containment, stat+sys). The BAT light curve shows a broad double-humped structure about 20 seconds long, with peaks around T+1s and T+14 s, with a peak count rate of ~1500 counts per second (15-350 keV) at ~1 second after the trigger.

XRT began observing at 06:36:13 UT, 80s after the BAT trigger. A bright uncatalogued source was found in the field, which XRT was able to centroid on. The on-board calculated coordinates of this source are: RA(J2000): 22:29:37.8, Dec(J2000): 19:33:32.7, with an uncertainty of 7 arcseconds radius (90% containment). This position lies 73 arcseconds from the center of the BAT error circle, and 6.2 arcseconds from the P60 position (GCN 3829).

The UVOT began observations at 06:36:13 UT, 80s after the BAT trigger. There is no new source detected in the preliminary UVOT data in the XRT error circle.