{
  "subject": "Swift Trigger 1404295: possible GRB 251015A",
  "bibcode": "2025GCN.42290....1K",
  "circularId": 42290,
  "submitter": "K.L. Page at U Leicester <klp5@leicester.ac.uk>",
  "body": "N. J. Klingler (GSFC/UMBC/CRESSTII), R. Brivio (INAF-OAB),\nS. Dichiara (PSU), M. Ferro (INAF-OAB), R. Gupta (NASA GSFC),\nN. P. M. Kuin (UCL-MSSL), A. Mei (INAF-OAB), K. L. Page (U Leicester),\nD. M. Palmer (LANL), T. Sbarrato (INAF-OAB) and M. H. Siegel (PSU)\nreport on behalf of the Neil Gehrels Swift Observatory Team:\n\nAt 14:17:23 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated a possible GRB 251015A (trigger=1404295).  Swift slewed\nimmediately to the location.\nThe BAT on-board calculated location is \nRA, Dec 245.007, -54.853 which is \n   RA(J2000) = 16h 20m 02s\n   Dec(J2000) = -54d 51' 10\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a complex\nstructure with a duration of about 10 sec.  The peak count rate\nwas ~800 counts/sec (15-350 keV), at ~0 sec after the trigger.\n\nThe XRT began observing the field at 14:19:31.3 UT, 127.6 seconds after\nthe BAT trigger. No source was detected in 877 s of promptly downlinked\ndata. We are waiting for the full dataset to detect and localise the\nXRT counterpart.\n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 870 seconds after the BAT trigger. No credible afterglow candidate has\nbeen found in the initial data products. The 2.7'x2.7' sub-image covers 25% of\nthe BAT error circle. Because of the density of catalogued stars, further\nanalysis is required to report an upper limit for any afterglow in the\nsub-image. The 8'x8' region for the list of sources generated on-board covers\n0.00% of the BAT error circle. No correction has been made for the large, but\nuncertain, extinction expected.\n\nDue to the marginal detection in the BAT image (6.53 sigma) and\nthe lack of an XRT counterpart, we believe that this is most likely\nto be a noise fluctuation, but might be a GRB.  Analysis\nof the complete downlinked dataset will be required to determine\nthe reality of this event.\n\nBurst Advocate for this burst is N. J. Klingler (noelklin AT umbc.edu).\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",
  "submittedHow": "email",
  "createdOn": 1760539483754,
  "eventId": "GRB 251015A"
}