{
  "bibcode": "2012GCN.13796....1Y",
  "body": "V. N. Yershov (UCL-MSSL), S. D. Barthelmy (GSFC),\nH. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (UCL-MSSL),\nC. J. Mountford (U Leicester), S. R. Oates (UCL-MSSL),\nK. L. Page (U Leicester) and M. H. Siegel (PSU) report on behalf of\nthe Swift Team:\n\nAt 05:16:06 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 120923A (trigger=534402).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 303.795, +6.235 which is \n   RA(J2000)  =  20h 15m 11s\n   Dec(J2000) = +06d 14' 05\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve shows several overlapping peaks\nwith a total duration of about 35 sec.  The peak count rate\nwas ~700 counts/sec (15-350 keV), at ~6 sec after the trigger. \n\nThe XRT began observing the field at 05:18:26.0 UT, 139.8 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source located at RA, Dec 303.79631, 6.22039 which is equivalent\nto:\n   RA(J2000)  = 20h 15m 11.11s\n   Dec(J2000) = +06d 13' 13.4\"\nwith an uncertainty of 4.1 arcseconds (radius, 90% containment). This\nlocation is 52 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 9.80\nx 10^20 cm^-2 (Kalberla et al. 2005). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 143 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 100% 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\n0.16. \n\nBurst Advocate for this burst is V. N. Yershov (vny AT mssl.ucl.ac.uk). \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": 13796,
  "createdOn": 1348378091000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "GRB 120923A: Swift detection of a burst",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 120923A"
}