{
  "bibcode": "2009GCN..8948....1E",
  "body": "P. A. Evans (U Leicester), S. D. Barthelmy (GSFC),\nA. P. Beardmore (U Leicester), D. N. Burrows (PSU),\nN. Gehrels (NASA/GSFC), S. T. Holland (CRESST/USRA/GSFC),\nR. Margutti (Univ Bicocca&OAB), C. B. Markwardt (CRESST/GSFC/UMD),\nF. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester),\nC. Pagani (PSU), K. L. Page (U Leicester), A. M. Parsons (GSFC),\nP. Romano (INAF-IASFPA), B. Sbarufatti (INAF-IASFPA),\nR. L. C. Starling (U Leicester), M. C. Stroh (PSU),\nT. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the\nSwift Team:\n\nAt 18:01:23 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 090308 (trigger=345777).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 183.526, -48.833 which is \n   RA(J2000) = 12h 14m 06s\n   Dec(J2000) = -48d 49' 57\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  This is an image trigger, but even so\nthe BAT light curve shows a weak peak at T+20 to T+35 sec. \nThe peak count rate was ~350 counts/sec (15-350 keV), at ~25 sec\nafter the trigger. \n\nThe XRT began observing the field at 18:03:30.4 UT, 126.9 seconds after\nthe BAT trigger. Using promptly downlinked data we find a fading,\nuncatalogued X-ray source with an enhanced position: RA, Dec 183.5017,\n-48.8169 which is equivalent to:\n   RA(J2000)  = 12h 14m 0.41s\n   Dec(J2000) = -48d 49' 00.9\"\nwith an uncertainty of 2.2 arcseconds (radius, 90% containment). This\nlocation is 81 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 (8.54e+20\ncm^-2, Kalberla et al. 2005), with an excess column of 1.8\n(+1.51/-1.36) x 10^21 cm^-2 (90% confidence). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 131 seconds after the BAT trigger. No credible afterglow candidate has\nbeen found in the initial data products. Because part of the 2.7'x2.7'\nsub-image was not received, there is no overlap with the XRT error circle. \nThe 8'x8' region for the list of sources generated on-board covers the entire\nXRT error circle. No correction has been\nmade for the expected extinction corresponding to E(B-V) of 0.11. \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": 8948,
  "createdOn": 1236536475000,
  "email": "scott@lheamail.gsfc.nasa.gov",
  "subject": "GRB 090308: Swift detection of a burst",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>",
  "eventId": "GRB 090308"
}