{
  "bibcode": "2009GCN..9386....1E",
  "body": "P. A. Evans (U Leicester), S. D. Barthelmy (GSFC),\nD. N. Burrows (PSU), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC),\nK. L. Page (U Leicester), D. M. Palmer (LANL),\nA. Rowlinson (U Leicester), M. H. Siegel (PSU),\nT. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the\nSwift Team:\n\nAt 01:54:44 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 090518 (trigger=352420).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 119.933, +0.768 which is \n   RA(J2000) = 07h 59m 44s\n   Dec(J2000) = +00d 46' 04\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve shows a single peak\nwith a duration of about 5 sec.  The peak count rate\nwas ~4000 counts/sec (15-350 keV), at ~1 sec after the trigger. \n\nThe XRT began observing the field at 01:55:57.8 UT, 73.5 seconds after\nthe BAT trigger. Using promptly downlinked data we find a fading,\nuncatalogued X-ray source located at RA, Dec 119.95519, 0.75892 which\nis equivalent to:\n   RA(J2000)  = 07h 59m 49.25s\n   Dec(J2000) = +00d 45' 32.1\"\nwith an uncertainty of 3.7 arcseconds (radius, 90% containment). This\nlocation is 86 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 (4.65e+20\ncm^-2, Kalberla et al. 2005), with an excess column of 4.9\n(+3.56/-2.94) x 10^21 cm^-2 (90% confidence). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 77 seconds after the BAT trigger. No credible afterglow candidate has\nbeen found in the initial data products. The 2.7'x2.7' sub-image covers none of\nthe XRT error circle. The 8'x8' region for the list of sources generated\non-board covers 100% of the XRT error circle. The list of sources is typically\ncomplete to about 18 mag. No correction has been made for the expected\nextinction corresponding to E(B-V) of 0.04. \n\nBurst Advocate for this burst is P. A. Evans (pae9 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": 9386,
  "createdOn": 1242612547000,
  "email": "scott@lheamail.gsfc.nasa.gov",
  "subject": "GRB 090518: Swift detection of a burst",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>",
  "eventId": "GRB 090518"
}