{
  "bibcode": "2011GCN.12279....1M",
  "body": "C. B. Markwardt (NASA/GSFC), S. D. Barthelmy (GSFC),\nW. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester),\nD. N. Burrows (PSU), J. R. Cummings (NASA/UMBC),\nS. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU),\nJ. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA),\nN. P. M. Kuin (UCL-MSSL), O. M. Littlejohns (U Leicester),\nF. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB),\nP. T. O'Brien (U Leicester), K. L. Page (U Leicester),\nT. A. Pritchard (PSU), A. Rowlinson (U Leicester),\nT. Sakamoto (NASA/UMBC), C. J. Saxton (UCL-MSSL), M. H. Siegel (PSU)\nand R. L. C. Starling (U Leicester) report on behalf of the Swift\nTeam:\n\nAt 20:37:49 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 110818A (trigger=500914).  Because of an Earth-limb\nobserving constraint, the slew to the burst was delayed by ~4 min. \nThe BAT on-board calculated location is \nRA, Dec 317.384, -63.970 which is \n   RA(J2000)  =  21h 09m 32s\n   Dec(J2000) = -63d 58' 10\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve shows several peaks\nwith a total duration of about 60 sec.  The peak count rate\nwas ~2000 counts/sec (15-350 keV), at ~7 sec after the trigger. \n\nThe XRT began observing the field at 20:44:09.7 UT, 380.4 seconds after\nthe BAT trigger. Using promptly downlinked data we find a fading,\nuncatalogued X-ray source with an enhanced position: RA, Dec 317.3382,\n-63.9814 which is equivalent to:\n   RA(J2000)  = 21h 09m 21.17s\n   Dec(J2000) = -63d 58' 53.1\"\nwith an uncertainty of 2.1 arcseconds (radius, 90% containment). This\nlocation is 83 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 (2.62 x\n10^20 cm^-2, Kalberla et al. 2005), with an excess column of 2\n(+1.14/-1.05) x 10^21 cm^-2 (90% confidence). \n\nUVOT took a finding chart exposure of 150 seconds with the U filter starting\n856 seconds after the BAT trigger. No credible afterglow candidate has been\nfound in the initial data products. The 2.7'x2.7' sub-image covers 100% of the\nXRT error circle. The typical 3-sigma upper limit has been about 19.2 mag. The\n8'x8' region for the list of sources generated on-board covers 100% of the XRT\nerror circle. No correction has been made for the expected extinction\ncorresponding to E(B-V) of 0.04. \n\nBurst Advocate for this burst is C. B. Markwardt (Craig.Markwardt 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": 12279,
  "createdOn": 1313701209000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "GRB 110818A: Swift detection of a burst",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 110818A"
}