{
  "bibcode": "2018GCN.23349....1M",
  "body": "M. J. Moss (George Washington University), A. D'Ai (INAF-IASFPA),\nV. D'Elia (SSDC), J.D. Gropp (PSU), J. A. Kennea (PSU),\nN. P. M. Kuin (UCL-MSSL), A. Y. Lien (GSFC/UMBC),\nK. L. Page (U Leicester), D. M. Palmer (LANL) and A. Tohuvavohu (PSU)\nreport on behalf of the Neil Gehrels Swift Observatory Team:\n\nAt 19:00:33 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 181020A (trigger=867987).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 13.967, -47.380 which is \n   RA(J2000) = 00h 55m 52s\n   Dec(J2000) = -47d 22' 47\"\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 ~12000 counts/sec (15-350 keV), at ~7 sec after the trigger. \n\nThe XRT began observing the field at 19:01:29.0 UT, 55.6 seconds after\nthe BAT trigger. XRT found a bright, uncatalogued X-ray source located\nat RA, Dec 13.9837, -47.3796 which is equivalent to:\n   RA(J2000)  = 00h 55m 56.09s\n   Dec(J2000) = -47d 22' 46.6\"\nwith an uncertainty of 4.8 arcseconds (radius, 90% containment). This\nlocation is 40 arcseconds from the BAT onboard position, within the BAT\nerror circle. No event data are yet available to determine the column\ndensity using X-ray spectroscopy. \n\nThe initial flux in the 2.5 s image was 6.04e-09 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 250 seconds with the U filter starting\n121 seconds after the BAT trigger. There is a candidate afterglow in the\nrapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t00:55:55.78 =  13.98240\n  DEC(J2000) = -47:22:51.8  = -47.38105\nwith a 90%-confidence error radius of about 0.76 arc sec. This position is 6.1\narc sec. from the center of the XRT error circle. The estimated magnitude is\n17.51 with a 1-sigma error of about  0.15. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.01. \n\nBurst Advocate for this burst is M. J. Moss (mikejmoss3 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/too.html.)",
  "circularId": 23349,
  "createdOn": 1540063183000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 181020A: Swift detection of a burst with an optical counterpart",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 181020A"
}