{
  "bibcode": "2012GCN.13886....1P",
  "body": "C. Pagani (U Leicester), S. D. Barthelmy (GSFC),\nW. H. Baumgartner (GSFC/UMBC), C. Gronwall (PSU), J. A. Kennea (PSU),\nC. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC),\nK. L. Page (U Leicester), D. M. Palmer (LANL), T. Sakamoto (AGU),\nB. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU) and\nT. N. Ukwatta (MSU) report on behalf of the Swift Team:\n\nAt 02:56:12 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 121024A (trigger=536580).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 70.467, -12.269 which is \n   RA(J2000)  =  04h 41m 52s\n   Dec(J2000) = -12d 16' 06\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve shows a few overlapping peaks\nwith a duration of about 15 sec.  The peak count rate\nwas ~3500 counts/sec (15-350 keV), at ~1 sec after the trigger. \n\nThe XRT began observing the field at 02:57:45.5 UT, 93.0 seconds after\nthe BAT trigger. XRT found a bright, uncatalogued X-ray source located\nat RA, Dec 70.4715, -12.2904 which is equivalent to:\n   RA(J2000)  = +04h 41m 53.16s\n   Dec(J2000) = -12d 17' 25.4\"\nwith an uncertainty of 5.5 arcseconds (radius, 90% containment). This\nlocation is 78 arcseconds from the BAT onboard position, within the BAT\nerror circle. No event data are yet available to determine the column\ndensity using X-ray spectroscopy. \n\nThe initial flux in the 2.5 s image was 1.10e-09 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 250 seconds with the U filter starting\n158 seconds after the BAT trigger. There is a candidate afterglow in the\nrapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t04:41:53.28 =  70.47201\n  DEC(J2000) = -12:17:26.8  = -12.29079\nwith a 90%-confidence error radius of about 0.78 arc sec. This position is 2.3\narc sec. from the center of the XRT error circle. The estimated magnitude is\n18.38 with a 1-sigma error of about  0.16. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.10. \n\nBurst Advocate for this burst is C. Pagani (cp232 AT star.le.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": 13886,
  "createdOn": 1351048377000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "GRB 121024A: Swift detection of a burst with an optical counterpart",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 121024A"
}