{
  "bibcode": "2012GCN.13716....1R",
  "body": "J. L. Racusin (NASA/GSFC), S. D. Barthelmy (GSFC),\nW. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),\nN. Gehrels (NASA/GSFC), S. T. Holland (STScI), J. A. Kennea (PSU),\nN. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC),\nK. L. Page (U Leicester), D. M. Palmer (LANL),\nT. Sakamoto (NASA/UMBC), B. Sbarufatti (INAF-OAB/PSU) and\nM. H. Siegel (PSU) report on behalf of the Swift Team:\n\nAt 00:24:23 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 120907A (trigger=532871).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 74.741, -9.314 which is \n   RA(J2000)  =  04h 58m 58s\n   Dec(J2000) = -09d 18' 48\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve shows a single pulse\nwith a duration of about 5 sec.  The peak count rate\nwas ~2000 counts/sec (15-350 keV), at ~2 sec after the trigger. \n\nThe XRT began observing the field at 00:25:45.1 UT, 82.0 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source with an enhanced position: RA, Dec 74.7494, -9.3143 which\nis equivalent to:\n   RA(J2000)  = 04h 58m 59.86s\n   Dec(J2000) = -09d 18' 51.3\"\nwith an uncertainty of 2.1 arcseconds (radius, 90% containment). This\nlocation is 29 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 5.35\nx 10^20 cm^-2 (Kalberla et al. 2005). \n\nUVOT took a finding chart exposure of 250 seconds with the U filter starting\n142 seconds after the BAT trigger. There is a candidate afterglow in the\nrapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t04:59:00.01 =  74.75005\n  DEC(J2000) = -09:18:54.2  =  -9.31505\nwith a 90%-confidence error radius of about 0.63 arc sec. This position is 4.6\narc sec. from the center of the XRT error circle. The estimated magnitude is\n17.63 with a 1-sigma error of about  0.15. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.09. \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": 13716,
  "createdOn": 1346978323000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "GRB 120907A: Swift detection of a burst with optical counterpart",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 120907A"
}