{
  "bibcode": "2009GCN.10130....1C",
  "body": "P.A. Curran (MSSL-UCL), W. H. Baumgartner (GSFC/UMBC),\nA. P. Beardmore (U Leicester), S. Campana (INAF-OAB),\nP. A. Evans (U Leicester), C. Guidorzi (U Ferrara),\nJ. A. Kennea (PSU), V. Mangano (INAF-IASFPA), J. Mao (INAF-OAB),\nP. T. O'Brien (U Leicester), K. L. Page (U Leicester),\nD. M. Palmer (LANL), A. Rowlinson (U Leicester) and M. H. Siegel (PSU)\nreport on behalf of the Swift Team:\n\nAt 08:49:22 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 091104 (trigger=374875).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 208.742, +47.398 which is \n   RA(J2000) = 13h 54m 58s\n   Dec(J2000) = +47d 23' 55\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  As is usual for an image trigger, there\nis no obvious variation in the immediately available light curve. \n\nThe XRT began observing the field at 08:51:34.2 UT, 131.5 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nuncatalogued X-ray source located at RA, Dec 208.75600, 47.41126 which\nis equivalent to:\n   RA(J2000)  = 13h 55m 1.44s\n   Dec(J2000) = +47d 24' 40.5\"\nwith an uncertainty of 4.0 arcseconds (radius, 90% containment). This\nlocation is 58 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\n1.72e+20 cm^-2 (Kalberla et al. 2005). \n\nThe initial flux in the 2.5 s image was 1.85e-09 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 150 seconds with\nthe White filter starting 139 seconds after the BAT trigger. No\ncredible afterglow candidate has been found in the initial data\nproducts. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. \nThe typical 3-sigma upper limit has been about 19.6 mag. The 8'x8'\nregion for the list of sources generated on-board covers 100% of the\nXRT error circle. The list of sources is typically complete to about\n18 mag. No correction has been made for the expected extinction\ncorresponding to E(B-V) of 0.01. \n\nBurst Advocate for this burst is P.A. Curran (pac AT mssl.ucl.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": 10130,
  "createdOn": 1257325703000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 091104: Swift detection of a burst",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 091104"
}