{
  "bibcode": "2018GCN.23482....1C",
  "body": "J. K. Cannizzo (NASA/UMBC), J.D. Gropp (PSU),\nK. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU)\nreport on behalf of the Neil Gehrels Swift Observatory Team:\n\nAt 06:36:24 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 181202A (trigger=874334).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 280.745, +27.951 which is \n   RA(J2000) = 18h 42m 59s\n   Dec(J2000) = +27d 57' 03\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a multi-peaked\nstructure with a duration of about 10 sec.  The peak count rate\nwas ~1100 counts/sec (15-350 keV), at ~1 sec after the trigger. \n\nThe XRT began observing the field at 06:37:49.8 UT, 85.4 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source located at RA, Dec 280.73563, 27.95894 which is equivalent\nto:\n   RA(J2000)  = 18h 42m 56.55s\n   Dec(J2000) = +27d 57' 32.2\"\nwith an uncertainty of 3.7 arcseconds (radius, 90% containment). This\nlocation is 41 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 http://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 1.67\nx 10^21 cm^-2 (Willingale et al. 2013). \n\nUVOT took a finding chart exposure of 250 seconds with the U filter starting 86\nseconds after the BAT trigger. There is a candidate afterglow in the rapidly\navailable 2.7'x2.7' sub-image at\n  RA(J2000)  =\t18:42:56.38 = 280.73490\n  DEC(J2000) = +27:57:35.0  =  27.95973\nwith a 90%-confidence error radius of about 0.63 arc sec. This position is 3.4\narc sec. from the center of the XRT error circle. The estimated magnitude is\n17.67 with a 1-sigma error of about  0.15. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.14. \n\nBurst Advocate for this burst is J. K. Cannizzo (cannizzo 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/too.html.)",
  "circularId": 23482,
  "createdOn": 1543733296000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 181202A: Swift detection of a burst with an optical counterpart",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 181202A"
}