{
  "body": "C. Salvaggio (INAF-OAB), R. Brivio (INAF-OAB), S. Dichiara (PSU),\nM. Ferro (INAF-OAB), R. Gupta (NASA GSFC), A. Y. Lien (U Tampa),\nF. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),\nA. Tohuvavohu (Caltech) and M. A. Williams (PSU) report on behalf of\nthe Neil Gehrels Swift Observatory Team:\n\nAt 21:43:16 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 241127A (trigger=1270788).  Swift slewed immediately to the burst.\nThe BAT on-board calculated location is \nRA, Dec 327.922, -56.685 which is \n   RA(J2000) = 21h 51m 41s\n   Dec(J2000) = -56d 41' 06\"\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 10 sec.  The peak count rate\nwas ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger.\n\nThe XRT began observing the field at 21:44:22.8 UT, 66.6 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nuncatalogued X-ray source located at RA, Dec 327.88355, -56.66459 which\nis equivalent to:\n   RA(J2000)  = 21h 51m 32.05s\n   Dec(J2000) = -56d 39' 52.5\"\nwith an uncertainty of 4.0 arcseconds (radius, 90% containment). This\nlocation is 105 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 (2.68 x\n10^20 cm^-2, Willingale et al. 2013), with an excess column of 6.1\n(+6.36/-4.83) x 10^21 cm^-2 (90% confidence). \n\nThe initial flux in the 2.5 s image was 2.12e-09 erg cm^-2 s^-1 (0.2-10\nkeV).\n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 484 seconds after the BAT trigger. There is a candidate afterglow in\nthe rapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t21:51:32.32 = 327.88467\n  DEC(J2000) = -56:39:55.1  = -56.66531\nwith a 90%-confidence error radius of about 0.61 arc sec. This position is 2.1\narc sec. from the center of the XRT error circle. The estimated magnitude is\n17.14 with a 1-sigma error of about  0.14. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.034.\n\nBurst Advocate for this burst is C. Salvaggio (chiara.salvaggio 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",
  "circularId": 38354,
  "eventId": "GRB 241127A",
  "subject": "GRB 241127A: Swift detection of a burst with an optical counterpart",
  "bibcode": "2024GCN.38354....1S",
  "createdOn": 1732744780712,
  "submittedHow": "email",
  "submitter": "K.L. Page at U Leicester <klp5@leicester.ac.uk>"
}