{
  "bibcode": "2015GCN.18186....1T",
  "body": "E. Troja (NASA/GSFC/UMCP), M. G. Bernardini (INAF-OAB),\nS. B. Cenko (GSFC), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC),\nP. A. Evans (U Leicester), A. Melandri (INAF-OAB) and\nK. L. Page (U Leicester) report on behalf of the Swift Team:\n\nAt 09:44:00 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 150821A (trigger=652847).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 341.906, -57.875 which is \n   RA(J2000) = 22h 47m 37s\n   Dec(J2000) = -57d 52' 30\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a multi-peaked\nstructure with a duration of at least 100 sec.  The peak count rate\nwas ~2840 counts/sec (15-350 keV), at ~35 sec after the trigger. \n\nThe XRT began observing the field at 09:48:04.2 UT, 243.3 seconds after\nthe BAT trigger. XRT found a bright, uncatalogued X-ray source located\nat RA, Dec 341.9129, -57.8941 which is equivalent to:\n   RA(J2000)  = +22h 47m 39.10s\n   Dec(J2000) = -57d 53' 38.8\"\nwith an uncertainty of 4.9 arcseconds (radius, 90% containment). This\nlocation is 70 arcseconds from the BAT onboard position, within the BAT\nerror circle. No event data are yet available to determine the column\ndensity using X-ray spectroscopy. \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 251 seconds after the BAT trigger. There is a candidate afterglow in\nthe rapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t22:47:39.18 = 341.91326\n  DEC(J2000) = -57:53:38.1  = -57.89393\nwith a 90%-confidence error radius of about 0.61 arc sec. This position is 0.9\narc sec. from the center of the XRT error circle. The estimated magnitude is\n16.48 with a 1-sigma error of about  0.14. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.02. \n\nBurst Advocate for this burst is E. Troja (eleonora.troja 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": 18186,
  "createdOn": 1440151152000,
  "email": "klp5@leicester.ac.uk",
  "subject": "GRB 150821A: Swift detection of a burst with an optical afterglow",
  "submitter": "Kim Page at U.of Leicester  <klp5@leicester.ac.uk>",
  "eventId": "GRB 150821A"
}