{
  "bibcode": "2016GCN.19979....1E",
  "body": "P.A. Evans (U Leicester), S. D. Barthelmy (GSFC),\nA. P. Beardmore (U Leicester), A. A. Breeveld (UCL-MSSL),\nD. N. Burrows (PSU), A. D'Ai (INAF-IASFPA), V. D'Elia (ASDC),\nJ. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC),\nF. E. Marshall (NASA/GSFC), B. Mingo (U Leicester),\nK. L. Page (U Leicester), P. Romano (INAF-IASFPA), T. Sakamoto (AGU),\nB. Sbarufatti (INAF-OAB/PSU) and E. Troja (NASA/GSFC/UMCP) report on\nbehalf of the Swift Team:\n\nAt 12:58:28 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 161004A (trigger=715084).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 263.171, -0.928, which is \n   RA(J2000)  =  17h 32m 41s\n   Dec(J2000) = -00d 55' 41\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve shows a couple of peaks\nwith a total duration of about 5 sec.  The peak count rate\nwas ~1800 counts/sec (15-350 keV), at ~0 sec after the trigger. \n\nThe XRT began observing the field at 12:59:49.3 UT, 80.7 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source located at RA, Dec 263.15298, -0.94831 which is equivalent\nto:\n   RA(J2000)  = 17h 32m 36.72s\n   Dec(J2000) = -00d 56' 53.9\"\nwith an uncertainty of 3.7 arcseconds (radius, 90% containment). This\nlocation is 97 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 in excess of the Galactic value (1.88 x\n10^21 cm^-2, Willingale et al. 2013), with an excess column of 4.1\n(+3.92/-2.99) x 10^21 cm^-2 (90% confidence). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 85 seconds after the BAT trigger. There is a candidate afterglow in\nthe list of sources generated on-board at\n  RA(J2000)  =\t17:32:36.59 = 263.15244\n  DEC(J2000) = -00:57:02.2  =  -0.95061\nwith a 90%-confidence error radius of about 1.10 arc sec. This position is 6.6\narc sec. from the center of the XRT error circle. The estimated magnitude is\n19.03. No correction has been made for the expected extinction corresponding to\nE(B-V) of 0.25. \n\nBurst Advocate for this burst is P.A. Evans (pae9 AT star.le.ac.uk). \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": 19979,
  "createdOn": 1475586614000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "GRB 161004A: Swift detection of a burst with a possible optical counterpart",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 161004A"
}