{
  "circularId": 37274,
  "body": "\nR. Gupta (NASA GSFC), R. Brivio (INAF-OAB), S. Dichiara (PSU),\nM. Ferro (INAF-OAB), J. A. Kennea (PSU), K. L. Page (U Leicester),\nD. M. Palmer (LANL) and T. Sbarrato (INAF-OAB) report on behalf of the\nNeil Gehrels Swift Observatory Team:\n\nAt 15:52:59 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 240825A (trigger=1250617).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 344.551, +1.036 which is \n   RA(J2000) = 22h 58m 12s\n   Dec(J2000) = +01d 02' 10\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a bright complex peak\nstructure with a duration of at least 10 sec.  The peak count rate\nwas ~160k counts/sec (15-350 keV), at ~1 sec after the trigger. \n\nThe XRT began observing the field at 15:54:22.9 UT, 83.1 seconds after\nthe BAT trigger. XRT found a bright, uncatalogued X-ray source located\nat RA, Dec 344.5691, 1.0253 which is equivalent to:\n   RA(J2000)  = 22h 58m 16.58s\n   Dec(J2000) = +01d 01' 31.1\"\nwith an uncertainty of 12.3 arcseconds (radius, 90% containment). This\nlocation is 75 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 92 seconds after the BAT trigger. There is a candidate afterglow in\nthe rapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t22:58:17.26 = 344.57192\n  DEC(J2000) = +01:01:36.7  =\t1.02686\nwith a 90%-confidence error radius of about 0.74 arc sec. This position is 11.6\narc sec. from the center of the XRT error circle. The estimated magnitude is\n15.57 with a 1-sigma error of about  0.14. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.063. \n\nBurst Advocate for this burst is R. Gupta (rahulbhu.c157 AT gmail.com). \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/)\n\n",
  "createdOn": 1724601857644,
  "subject": "GRB 240825A: Swift detection of a burst with a bright optical counterpart",
  "bibcode": "2024GCN.37274....1G",
  "submitter": "David Palmer at LANL <palmer@lanl.gov>",
  "eventId": "GRB 240825A",
  "submittedHow": "email"
}