{
  "bibcode": "2015GCN.18478....1M",
  "body": "A. Maselli (INAF-IASFPA), A. D'Ai (INAF-IASFPA),\nA. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL),\nB. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU),\nM. Stamatikos (OSU/NASA/GSFC) and T. N. Ukwatta (LANL) report on\nbehalf of the Swift Team:\n\nAt 03:58:24 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 151027A (trigger=661775).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 272.491, +61.381 which is \n   RA(J2000) = 18h 09m 58s\n   Dec(J2000) = +61d 22' 51\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a complex\npeaked structure lasting at least 150 seconds.  The peak count rate\nwas ~6000 counts/sec (15-350 keV), at ~110 sec after the trigger. \n\nThe XRT began observing the field at 03:59:51.1 UT, 87.0 seconds after\nthe BAT trigger. XRT found a bright, uncatalogued X-ray source located\nat RA, Dec 272.4886, 61.3515 which is equivalent to:\n   RA(J2000)  = +18h 09m 57.26s\n   Dec(J2000) = +61d 21' 05.4\"\nwith an uncertainty of 4.8 arcseconds (radius, 90% containment). This\nlocation is 106 arcseconds from the BAT onboard position, within the\nBAT error circle. No event data are yet available to determine the\ncolumn density using X-ray spectroscopy. \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 95 seconds after the BAT trigger. There is a candidate afterglow in\nthe rapidly available 2.7'x2.7' sub-image at\nRA(J2000) =\t18:09:56.68 = 272.48615\nDEC(J2000) = +61:21:13.4 = 61.35373\nwith a 90%-confidence error radius of about 0.61 arc sec. This position is 9.06\narc sec. from the center of the XRT error circle. The estimated magnitude is\n14.46 with a 1-sigma error of about 0.14. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.05. \n\nBurst Advocate for this burst is A. Maselli (maselli 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.)",
  "circularId": 18478,
  "createdOn": 1445919391000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 151027A: Swift detection of a burst with a bright optical afterglow",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 151027A"
}