{
  "bibcode": "2016GCN.20296....1D",
  "body": "A. D'Ai (INAF-IASFPA), J. A. Kennea (PSU),\nH. A. Krimm (CRESST/NSF/USRA), N. P. M. Kuin (UCL-MSSL),\nF. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),\nD. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU) and\nM. H. Siegel (PSU) report on behalf of the Swift Team:\n\nAt 18:48:39 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 161219B (trigger=727541).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 91.717, -26.790 which is \n   RA(J2000) = 06h 06m 52s\n   Dec(J2000) = -26d 47' 23\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a single triangle-\nshaped structure with a duration of about 10 sec.  The peak count rate\nwas ~3900 counts/sec (15-350 keV), at ~2 sec after the trigger. \n\nThe XRT began observing the field at 18:50:27.5 UT, 108.2 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source with an enhanced position: RA, Dec 91.7140, -26.7915 which\nis equivalent to:\n   RA(J2000)  = 06h 06m 51.35s\n   Dec(J2000) = -26d 47' 29.4\"\nwith an uncertainty of 2.2 arcseconds (radius, 90% containment). This\nlocation is 11 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. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density in excess of the Galactic value (3.06 x\n10^20 cm^-2, Willingale et al. 2013), with an excess column of 4\n(+2.38/-1.96) x 10^21 cm^-2 (90% confidence). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 111 seconds after the BAT trigger. There is a candidate afterglow in\nthe rapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t06:06:51.41 = 91.71421\n  DEC(J2000) = -26:47:29.2  = -26.79144\nwith a 90%-confidence error radius of about 0.5 arc sec. This position is 0.9\narc sec. from the center of the XRT error circle. The estimated magnitude is\n16.10 with a 1-sigma error of about  0.03. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.03. \n\nBurst Advocate for this burst is A. D'Ai (antonino.dai AT ifc.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/too.html.)\n\n[GCN OPS NOTE(20dec16): Per author's request, the \"-29:47:29.2\"\nin the 4th paragraph was changed to \"-26:47:29.2\".]",
  "circularId": 20296,
  "createdOn": 1482174423000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 161219B: Swift detection of a burst with an optical afterglow",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 161219B"
}