{
  "bibcode": "2020GCN.28761....1M",
  "body": "F. E. Marshall (NASA/GSFC), M. G. Bernardini (INAF-OAB),\nP. D'Avanzo (INAF-OAB), J.D. Gropp (PSU), N. J. Klingler (PSU),\nN. P. M. Kuin (UCL-MSSL), S. Laha (GSFC/UMBC/CRESST),\nA. Melandri (INAF-OAB), D. M. Palmer (LANL), T. Sbarrato (INAF-OAB)\nand A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels\nSwift Observatory Team:\n\nAt 02:48:59 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 201024A (trigger=1001514).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 125.948, +3.377 which is \n   RA(J2000) = 08h 23m 47s\n   Dec(J2000) = +03d 22' 38\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a single peak\nstructure with a duration of about 5 sec.  The peak count rate\nwas ~1200 counts/sec (15-350 keV), at ~0 sec after the trigger. \n\nThe XRT began observing the field at 02:50:14.0 UT, 74.9 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nuncatalogued X-ray source with an enhanced position: RA, Dec 125.9521,\n3.3537 which is equivalent to:\n   RA(J2000)  = 08h 23m 48.50s\n   Dec(J2000) = +03d 21' 13.4\"\nwith an uncertainty of 2.1 arcseconds (radius, 90% containment). This\nlocation is 85 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 3.64\nx 10^20 cm^-2 (Willingale et al. 2013). \n\nThe initial flux in the 2.5 s image was 6.41e-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 495 seconds after the BAT trigger. There is a candidate afterglow in\nthe rapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t08:23:48.55 = 125.95229\n  DEC(J2000) = +03:21:14.5  =\t3.35403\nwith a 90%-confidence error radius of about 0.62 arc sec. This position is 0.7\narc sec. from the center of the XRT error circle. The estimated magnitude is\n17.85 with a 1-sigma error of about  0.14. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.03. \n\nBurst Advocate for this burst is F. E. Marshall (marshall AT milkyway.gsfc.nasa.gov). \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/)",
  "circularId": 28761,
  "createdOn": 1603509012000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 201024A: Swift detection of a burst with an optical afterglow",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 201024A"
}