{
  "circularId": 42113,
  "submittedHow": "email",
  "bibcode": "2025GCN.42113....1P",
  "eventId": "GRB 251005C",
  "editedBy": "Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov>",
  "subject": "GRB 251005C: Swift detection of a burst",
  "editedOn": 1759694467500,
  "createdOn": 1759681407185,
  "version": 3,
  "submitter": "K.L. Page at U Leicester <klp5@leicester.ac.uk>",
  "body": "K. L. Page (U Leicester), S. Dichiara (PSU), R. Gupta (NASA GSFC),\nJ. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL) and M. J. Moss (GSFC)\nreport on behalf of the Neil Gehrels Swift Observatory Team:\n\nAt 16:06:53 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 251005C (trigger=1401726).  Swift slewed immediately to the burst.\nThe BAT on-board calculated location is \nRA, Dec 75.673, +16.882 which is \n   RA(J2000) = 05h 02m 42s\n   Dec(J2000) = +16d 52' 54\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a double-peaked\nstructure with a duration of about 2 sec.  The peak count rate\nwas ~4,500 counts/sec (15-350 keV), at ~1 sec after the trigger.\n\nThe XRT began observing the field at 16:08:52.2 UT, 118.3 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source with an enhanced position: RA, Dec 75.68331, 16.88007\nwhich is equivalent to:\n   RA(J2000)  = 05h 02m 44.00s\n   Dec(J2000) = +16d 52' 48.3\"\nwith an uncertainty of 2.1 arcseconds (radius, 90% containment). This\nlocation is 36 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 (3.19 x\n10^21 cm^-2, Willingale et al. 2013), with an excess column of 5\n(+3.76/-3.16) x 10^21 cm^-2 (90% confidence).\n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 122 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 100% of\nthe XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag.\nThe 8'x8' region for the list of sources generated on-board covers 100% of the\nXRT error circle. The list of sources is typically complete to about 18 mag. No\ncorrection has been made for the expected extinction corresponding to E(B-V) of\n0.461.\n\nBurst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk).\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",
  "format": "text/plain"
}