{
  "submitter": "David Palmer at LANL <palmer@lanl.gov>",
  "eventId": "GRB 251007B",
  "bibcode": "2025GCN.42147....1M",
  "subject": "GRB 251007B: Swift detection of a burst",
  "submittedHow": "email",
  "circularId": 42147,
  "createdOn": 1759867503741,
  "body": "A. Melandri (INAF-OAR), E. Ambrosi (INAF-IASFPA),\nA. D'Ai (INAF-IASFPA), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU),\nR. Gupta (NASA GSFC), N. J. Klingler (GSFC/UMBC/CRESSTII),\nN. P. M. Kuin (UCL-MSSL) and M. H. Siegel (PSU) report on behalf of\nthe Neil Gehrels Swift Observatory Team:\n\nAt 19:43:06 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 251007B (trigger=1402467).  Swift slewed immediately to the burst.\nThe BAT on-board calculated location is \nRA, Dec 102.117, -10.303 which is \n   RA(J2000) = 06h 48m 28s\n   Dec(J2000) = -10d 18' 11\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  Due to the continued on-board processing of the\nprevious burst (GRB 251007A) the BAT lightcurve is not immediately available.\n\nThe XRT began observing the field at 19:45:35.0 UT, 148.2 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source located at RA, Dec 102.13232, -10.30328 which is\nequivalent to:\n   RA(J2000)  = 06h 48m 31.76s\n   Dec(J2000) = -10d 18' 11.8\"\nwith an uncertainty of 3.7 arcseconds (radius, 90% containment). This\nlocation is 54 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.  We\ncannot determine whether the source is fading at the present time. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density consistent with the Galactic value of 5.99\nx 10^21 cm^-2 (Willingale et al. 2013).\n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 151 seconds after the BAT trigger. No credible afterglow candidate has\nbeen found in the initial data products. The 2.7'x2.7' sub-image processing\nFAILED because of no aspect solution. Results from the list of sources\ngenerated on-board are not available at this time. No correction has been made\nfor the expected extinction corresponding to E(B-V) of 0.785.\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"
}