{
  "circularId": 37722,
  "submitter": "K.L. Page at U Leicester <klp5@leicester.ac.uk>",
  "subject": "GRB 241006A: Swift detection of a burst",
  "bibcode": "2024GCN.37722....1G",
  "createdOn": 1728252446408,
  "eventId": "GRB 241006A",
  "submittedHow": "email",
  "body": "R. Gupta (NASA GSFC), M. J. Moss (GSFC), K. L. Page (U Leicester),\nD. M. Palmer (LANL) and B. Sbarufatti (INAF-OAB) report on behalf of\nthe Neil Gehrels Swift Observatory Team:\n\nAt 21:51:58 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 241006A (trigger=1258721).  Swift slewed immediately to the burst.\nThe BAT on-board calculated location is \nRA, Dec 304.794, -40.796 which is \n   RA(J2000) = 20h 19m 11s\n   Dec(J2000) = -40d 47' 44\"\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 30 sec.  The peak count rate\nwas ~700 counts/sec (15-350 keV), at ~-1 sec after the trigger.\n\nThe XRT began observing the field at 21:54:23.5 UT, 145.3 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nuncatalogued X-ray source with an enhanced position: RA, Dec 304.74258,\n-40.80514 which is equivalent to:\n   RA(J2000)  = 20h 18m 58.22s\n   Dec(J2000) = -40d 48' 18.5\"\nwith an uncertainty of 1.9 arcseconds (radius, 90% containment). This\nlocation is 143 arcseconds from the BAT onboard position, within the\nBAT error circle. This position may be improved as more data are\nreceived; the latest position is available at\nhttps://www.swift.ac.uk/sper.  We cannot determine whether the source\nis fading at the present time. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density in excess of the Galactic value (4.92 x\n10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.5\n(+3.24/-2.77) x 10^21 cm^-2 (90% confidence). \n\nThe initial flux in the 2.5 s image was 4.75e-10 erg cm^-2 s^-1 (0.2-10\nkeV).\n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 349 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 none of\nthe XRT error circle. The 8'x8' region for the list of sources generated\non-board covers 100% of the XRT error circle. The list of sources is typically\ncomplete to about 18 mag. No correction has been made for the expected\nextinction corresponding to E(B-V) of 0.065.\n\nBurst Advocate for this burst is R. Gupta (rahulbhu.c157 AT gmail.com).\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"
}