{
  "bibcode": "2012GCN.14007....1O",
  "body": "S. R. Oates (UCL-MSSL), S. D. Barthelmy (GSFC),\nH. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (UCL-MSSL),\nC. B. Markwardt (NASA/GSFC), K. L. Page (U Leicester),\nM. H. Siegel (PSU) and M. Stamatikos (OSU/NASA/GSFC) report on behalf\nof the Swift Team:\n\nAt 05:05:37 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 121128A (trigger=539866).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 300.583, +54.321 which is \n   RA(J2000) = 20h 02m 20s\n   Dec(J2000) = +54d 19' 17\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a multi-peaked\nstructure with a duration of about 40 sec.  The peak count rate\nwas ~20,000 counts/sec (15-350 keV), at ~20 sec after the trigger. \n\nThe XRT began observing the field at 05:06:54.3 UT, 77.2 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nuncatalogued X-ray source located at RA, Dec 300.60067, 54.30060 which\nis equivalent to:\n   RA(J2000)  = 20h 02m 24.16s\n   Dec(J2000) = +54d 18' 02.2\"\nwith an uncertainty of 3.9 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. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density consistent with the Galactic value of 2.08\nx 10^21 cm^-2 (Kalberla et al. 2005). \n\nThe initial flux in the 2.5 s image was 1.58e-09 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 85 seconds after the BAT trigger. There is a candidate afterglow in\nthe rapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t20:02:24.01 = 300.60004\n  DEC(J2000) = +54:17:59.2  =  54.29977\nwith a 90%-confidence error radius of about 0.61 arc sec. This position is 5.5\narc sec. from the center of the XRT error circle. The estimated magnitude is\n16.11 with a 1-sigma error of about  0.14. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.31. \n\nBurst Advocate for this burst is S. R. Oates (sro 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": 14007,
  "createdOn": 1354079880000,
  "email": "sro@mssl.ucl.ac.uk",
  "subject": "GRB 121128A: Swift detection of a burst with an optical counterpart",
  "submitter": "Samantha Oates at MSSL  <sro@mssl.ucl.ac.uk>",
  "eventId": "GRB 121128A"
}