{
  "bibcode": "2009GCN..9768....1S",
  "body": "M. Stamatikos (NASA/ORAU), J. R. Cummings (NASA/UMBC),\nP. A. Evans (U Leicester), C. Gronwall (PSU),\nC. Guidorzi (U Ferrara), C. B. Markwardt (CRESST/GSFC/UMD),\nP. T. O'Brien (U Leicester), K. L. Page (U Leicester),\nD. M. Palmer (LANL) and R. L. C. Starling (U Leicester) report on\nbehalf of the Swift Team:\n\nAt 06:02:08 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 090812 (trigger=359711).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 353.194, -10.595 which is \n   RA(J2000) = 23h 32m 47s\n   Dec(J2000) = -10d 35' 39\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a triple-peaked\nstructure with a duration of about 70 sec.  The peak count rate\nwas ~6500 counts/sec (15-350 keV), at ~25 sec after the trigger. \n\nThe XRT began observing the field at 06:03:25.7 UT, 76.8 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nuncatalogued X-ray source located at RA, Dec 353.20133, -10.60457 which\nis equivalent to:\n   RA(J2000)  = 23h 32m 48.32s\n   Dec(J2000) = -10d 36' 16.5\"\nwith an uncertainty of 3.7 arcseconds (radius, 90% containment). This\nlocation is 43 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\n2.26e+20 cm^-2 (Kalberla et al. 2005). \n\nThe initial flux in the 2.5 s image was 4.95e-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\n298 seconds after the BAT trigger. There is a candidate afterglow in the\nrapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t23:32:48.53 = 353.20222\n  DEC(J2000) = -10:36:17.3  = -10.60481\nwith a 90%-confidence error radius of about 0.78 arc sec. This position is 5.1\narc sec. from the center of the XRT error circle. The estimated magnitude is\n18.62 with a 1-sigma error of about 0.16. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.02. \n\nBurst Advocate for this burst is M. Stamatikos (michael AT milkyway.gsfc.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": 9768,
  "createdOn": 1250058046000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 090812: Swift detection of a burst with an optical counterpart",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 090812"
}