{
  "bibcode": "2009GCN.10034....1S",
  "body": "M. Stamatikos (OSU/NASA/GSFC), D. N. Burrows (PSU),\nJ. R. Cummings (NASA/UMBC), V. D'Elia (ASDC), N. Gehrels (NASA/GSFC),\nC. Gronwall (PSU), C. Guidorzi (U Ferrara),\nS. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),\nW.B Landsman (GSFC), C. B. Markwardt (CRESST/GSFC/UMD),\nF. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester),\nD. M. Palmer (LANL), M. Perri (ASDC), J. L. Racusin (NASA/GSFC/ORAU)\nand G. Stratta (ASDC) report on behalf of the Swift Team:\n\nAt 20:48:19 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 091018 (trigger=373172).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 32.211, -57.526 which is \n   RA(J2000) = 02h 08m 51s\n   Dec(J2000) = -57d 31` 34``\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a single smooth\nFRED peak a duration of about 10 sec.  The peak count rate\nwas ~16000 counts/sec (15-350 keV), at ~2 sec after the trigger. \n\nThe XRT began observing the field at 20:49:20.5 UT, 60.9 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nuncatalogued X-ray source located at RA, Dec 32.18587, -57.54749 which\nis equivalent to:\n   RA(J2000)  = 02h 08m 44.61s\n   Dec(J2000) = -57d 32' 51.0\"\nwith an uncertainty of 3.7 arcseconds (radius, 90% containment). This\nlocation is 91 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 in excess of the Galactic value (2.81e+20\ncm^-2, Kalberla et al. 2005), with an excess column of 1.4\n(+1.00/-0.93) x 10^21 cm^-2 (90% confidence). \n\nThe initial flux in the 2.5 s image was 4.40e-10 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 68 seconds after the BAT trigger. There is a candidate afterglow in\nthe rapidly available 2.7`x2.7` sub-image at\n  RA(J2000)  =\t02:08:44.61 = 32.18588\n  DEC(J2000) = -57:32:53.8  = -57.54827\nwith a 90%-confidence error radius of about 0.61 arc sec. This position is 3.8\narc sec. from the center of the XRT error circle. The estimated magnitude is\n14.60 with a 1-sigma error of about 0.14. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.03. \n\nBurst Advocate for this burst is M. Stamatikos (Michael.Stamatikos-1 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": 10034,
  "createdOn": 1255900114000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 091018: Swift detection of a burst with optical afterglow",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 091018"
}