{
  "subject": "GRB 251001B: Swift detection of a burst",
  "createdOn": 1759329882661,
  "submitter": "K.L. Page at U Leicester <klp5@leicester.ac.uk>",
  "body": "A. P. Beardmore (U Leicester), J. A. Kennea (PSU), M. J. Moss (GSFC)\nand K. L. Page (U Leicester) report on behalf of the Neil Gehrels\nSwift Observatory Team:\n\nAt 14:17:20 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 251001B (trigger=1400467).  Swift slewed immediately to the burst.\nThe BAT on-board calculated location is \nRA, Dec 42.665, -23.020 which is \n   RA(J2000) = 02h 50m 40s\n   Dec(J2000) = -23d 01' 09\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a single-peaked\nstructure with a duration of about 25 sec.  The peak count rate\nwas ~2,000 counts/sec (15-350 keV), at ~4 sec after the trigger.\n\nThe XRT began observing the field at 14:19:17.0 UT, 116.5 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source with an enhanced position: RA, Dec 42.65098, -23.02014\nwhich is equivalent to:\n   RA(J2000)  = 02h 50m 36.24s\n   Dec(J2000) = -23d 01' 12.5\"\nwith an uncertainty of 1.9 arcseconds (radius, 90% containment). This\nlocation is 46 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 consistent with the Galactic value of 2.65\nx 10^20 cm^-2 (Willingale et al. 2013).\n\nUVOT took a finding chart exposure of nominal 150.000 seconds with the White\nfilter starting 860 seconds after the BAT trigger. No credible afterglow\ncandidate has been found in the initial data products. Data from the 2.7'x2.7'\nsub-image are not available at this time. The 8'x8' region for the list of\nsources generated on-board covers 100% of the XRT error circle. The list of\nsources is typically complete to about 18 mag. No correction has been made for\nthe expected extinction corresponding to E(B-V) of 0.023.\n\nBurst Advocate for this burst is A. P. Beardmore (apb AT star.le.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",
  "circularId": 42039,
  "bibcode": "2025GCN.42039....1B",
  "submittedHow": "email",
  "eventId": "GRB 251001B"
}