{
  "bibcode": "2009GCN..8964....1E",
  "body": "P. A. Evans (U Leicester), W. H. Baumgartner (GSFC/UMBC),\nD. N. Burrows (PSU), C. Guidorzi (U Ferrara),\nS. T. Holland (CRESST/USRA/GSFC), W.B Landsman (GSFC),\nF. E. Marshall (NASA/GSFC), C. Pagani (PSU),\nK. L. Page (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC),\nB. A. Rowlinson (U Leicester), T. Sakamoto (NASA/UMBC),\nM. H. Siegel (PSU), T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU)\nreport on behalf of the Swift Team:\n\nAt 23:29:13 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 090309 (trigger=345945).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 284.981, -25.264 which is \n   RA(J2000) = 18h 59m 55s\n   Dec(J2000) = -25d 15' 50\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a peak with a \nwith a duration of about 3 sec.  There is a hint of a secondary peak \naround T+25 sec with a duration of 10 sec.  The peak count rate\nwas ~1400 counts/sec (15-350 keV), at ~1 sec after the trigger. \n\nThe XRT began observing the field at 23:30:32.5 UT, 79.3 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source with an enhanced position: RA, Dec 284.9730, -25.2611\nwhich is equivalent to:\n   RA(J2000)  = 18h 59m 53.51s\n   Dec(J2000) = -25d 15' 39.8\"\nwith an uncertainty of 3.3 arcseconds (radius, 90% containment). This\nlocation is 28 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\n1.07e+21 cm^-2 (Kalberla et al. 2005). \n\n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 81 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 100% of\nthe XRT error circle.  The typical upper limit for this image is approximately\nwhite = 19 mag. No correction has been made for the expected extinction\ncorresponding to E(B-V) of 0.23. \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": 8964,
  "createdOn": 1236642652000,
  "email": "dxb15@psu.edu",
  "subject": "GRB 090309: Swift detection of a burst",
  "submitter": "David Burrows at PSU/Swift  <dxb15@psu.edu>",
  "eventId": "GRB 090309"
}