{
  "body": "\nA. Melandri (INAF-OAR), E. Ambrosi (INAF-IASFPA),\nA. D'Ai (INAF-IASFPA), S. Dichiara (PSU), J.D. Gropp (PSU),\nJ. A. Kennea (PSU) and D. M. Palmer (LANL) report on behalf of the\nNeil Gehrels Swift Observatory Team:\n\nAt 14:17:19 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 231111A (trigger=1195887).  Swift slewed immediately to\nthe event. The BAT on-board calculated location is \nRA, Dec 290.234, +52.447 which is \n  RA(J2000) = 19h 20m 56s\n  Dec(J2000) = +52d 26' 49\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  Due to a telemetry outage, there is no\nimmediately available BAT lightcurve information.  However the\ntrigger information indicates an initial count rate of\n3100 counts/s (25-100 keV) on a 1 second timescale. \n\nThe XRT began observing the field at 14:18:59.3 UT, 99.6 seconds after\nthe BAT trigger. XRT found a bright, uncatalogued X-ray source located\nat RA, Dec 290.1915, 52.4383 which is equivalent to:\n   RA(J2000)  = 19h 20m 45.96s\n   Dec(J2000) = +52d 26' 17.9\"\nwith an uncertainty of 5.5 arcseconds (radius, 90% containment). This\nlocation is 98 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 238 seconds with the U filter starting\n164 seconds after the BAT trigger. There is a candidate afterglow in the\nrapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t19:20:45.24 = 290.18848\n  DEC(J2000) = +52:26:10.5  =  52.43626\nwith a 90%-confidence error radius of about 0.62 arc sec. This position is 9.9\narc sec. from the center of the XRT error circle. The estimated magnitude is\n16.51 with a 1-sigma error of about  0.14. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.117. \n\nBurst Advocate for this burst is A. Melandri (andrea.melandri AT inaf.it). \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",
  "circularId": 34981,
  "submittedHow": "email",
  "bibcode": "2023GCN.34981....1M",
  "submitter": "Jamie Kennea at Penn State <jak51@psu.edu>",
  "subject": "GRB 231111A: Swift detection of a burst with an optical counterpart",
  "createdOn": 1699713213033,
  "eventId": "GRB 231111A"
}