{
  "bibcode": "2012GCN.13566....1R",
  "body": "J. L. Racusin (NASA/GSFC), A. P. Beardmore (U Leicester),\nD. N. Burrows (PSU), P. A. Evans (U Leicester),\nC. Guidorzi (U Ferrara), J. A. Kennea (PSU),\nH. A. Krimm (CRESST/GSFC/USRA), O. M. Littlejohns (U Leicester) and\nK. L. Page (U Leicester) report on behalf of the Swift Team:\n\nAt 11:06:06 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 120803B (trigger=529606).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 314.224, +53.282 which is \n   RA(J2000) = 20h 56m 54s\n   Dec(J2000) = +53d 16' 57\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a single-peaked\nstructure with a duration of about 30 sec.  The peak count rate\nwas ~3000 counts/sec (15-350 keV), at ~0 sec after the trigger. \n\nThe XRT began observing the field at 11:07:22.4 UT, 75.5 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source located at RA, Dec 314.23606, 53.30380 which is equivalent\nto:\n   RA(J2000)  = 20h 56m 56.65s\n   Dec(J2000) = +53d 18' 13.7\"\nwith an uncertainty of 3.7 arcseconds (radius, 90% containment). This\nlocation is 82 arcseconds from the BAT onboard position, within the BAT\nerror circle. This position may be improved as more data are received;\nthe latest position is available at http://www.swift.ac.uk/sper.  We\ncannot determine whether the source is fading at the present time. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density consistent with the Galactic value of 5.67\nx 10^21 cm^-2 (Kalberla et al. 2005). \n\nUVOT took a finding chart exposure of 149 seconds with the White filter\nstarting 78 seconds after the BAT trigger. No credible afterglow candidate has\nbeen found in the initial data products. The 2.7'x2.7' sub-image covers 3.5% of\nthe XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. \nThe 8'x8' region for the list of sources generated on-board covers 100% of the\nXRT error circle. The list of sources is typically complete to about 18 mag. No\ncorrection has been made for the expected extinction corresponding to E(B-V) of\n1.71. \n\nBurst Advocate for this burst is J. L. Racusin (judith.racusin AT nasa.gov). \nPlease contact the BA by email if you require additional information\nregarding Swift followup of this burst. In extremely urgent cases, after\ntrying the Burst Advocate, you can contact the Swift PI by phone (see\nSwift TOO web site for information: http://www.swift.psu.edu/too.html.)",
  "circularId": 13566,
  "createdOn": 1343992909000,
  "email": "kennea@swift.psu.edu",
  "subject": "GRB 120803B: Swift detection of a burst",
  "submitter": "Jamie A. Kennea at PSU/Swift-XRT  <kennea@swift.psu.edu>",
  "eventId": "GRB 120803B"
}