{
  "bibcode": "2013GCN.15139....1H",
  "body": "L. M. Z. Hagen (PSU), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC),\nN. Gehrels (NASA/GSFC), D. Grupe (PSU), J. A. Kennea (PSU),\nV. Mangano (PSU), F. E. Marshall (NASA/GSFC),\nC. J. Mountford (U Leicester), P. T. O'Brien (U Leicester),\nD. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU),\nE. Troja (NASA/GSFC/UMCP) and B.-B. Zhang (UAH) report on behalf of\nthe Swift Team:\n\nAt 13:04:16 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 130831A (trigger=568849).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 358.649, +29.448 which is \n   RA(J2000) = 23h 54m 36s\n   Dec(J2000) = +29d 26' 53\"\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 50 sec.  The peak count rate\nwas ~10000 counts/sec (15-350 keV), at ~2 sec after the trigger. \n\nThe XRT began observing the field at 13:06:22.3 UT, 125.8 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nfading, uncatalogued X-ray source located at RA, Dec 358.62398,\n29.42849 which is equivalent to:\n   RA(J2000)  = 23h 54m 29.76s\n   Dec(J2000) = +29d 25' 42.6\"\nwith an uncertainty of 3.7 arcseconds (radius, 90% containment). This\nlocation is 105 arcseconds from the BAT onboard position, within the\nBAT error circle. This position may be improved as more data are\nreceived; the latest position is available at\nhttp://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 4.80\nx 10^20 cm^-2 (Kalberla et al. 2005). \n\nThe initial flux in the 2.5 s image was 8.87e-10 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 250 seconds with the U filter starting\n190 seconds after the BAT trigger. There is a candidate afterglow in the\nrapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t23:54:29.89 = 358.62453\n  DEC(J2000) = +29:25:46.2  =  29.42950\nwith a 90%-confidence error radius of about 0.74 arc sec. This position is 5.8\narc sec. from the center of the XRT error circle. The estimated magnitude is\n14.56 with a 1-sigma error of about  0.14. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.04. \n\nBurst Advocate for this burst is L. M. Z. Hagen (lea.zernow.hagen AT gmail.com). \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": 15139,
  "createdOn": 1377955271000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 130831A: Swift detection of a burst with an optical counterpart",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 130831A"
}