{
  "body": "A. D'Ai (INAF-IASFPA), E. Ambrosi (INAF-IASFPA),\nV. D'Elia (SSDC & INAF-OAR), R. Gupta (NASA GSFC),\nN. P. M. Kuin (UCL-MSSL), A. Melandri (INAF-OAR),\nK. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU)\nreport on behalf of the Neil Gehrels Swift Observatory Team:\n\nAt 07:08:22.33 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 251011B (trigger=1403191).  Swift slewed immediately to the burst.\nThe BAT on-board calculated location is \nRA, Dec 13.287, -62.032 which is \n   RA(J2000) = 00h 53m 09s\n   Dec(J2000) = -62d 01' 55\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty). The BAT light curve showed a complex structure\nwith a duration of about 150 seconds.  The peak count rate was ~3000\ncounts/sec (15-350 keV) at ~0 sec after the trigger.\n\nThe XRT began observing the field at 07:09:58.8 UT, 96.5 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nfading, uncatalogued X-ray source located at RA, Dec 13.23523,\n-62.03269 which is equivalent to:\n   RA(J2000)  = 00h 52m 56.46s\n   Dec(J2000) = -62d 01' 57.7\"\nwith an uncertainty of 3.8 arcseconds (radius, 90% containment). This\nlocation is 87 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 https://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 (1.68 x\n10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.5\n(+3.47/-2.92) x 10^21 cm^-2 (90% confidence). \n\nThe initial flux in the 2.5 s image was 1.95e-09 erg cm^-2 s^-1 (0.2-10\nkeV).\n\nUVOT data are unavailable at this time.\n\nBurst Advocate for this burst is A. D'Ai (antonino.dai 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",
  "subject": "GRB 251011B: Swift detection of a burst",
  "eventId": "GRB 251011B",
  "submitter": "Antonino D'Ai' at INAF <antonino.dai@inaf.it>",
  "createdOn": 1760167761645,
  "bibcode": "2025GCN.42197....1D",
  "circularId": 42197,
  "submittedHow": "email"
}