{
  "bibcode": "2017GCN.21864....1L",
  "body": "S. J. LaPorte (PSU), J. A. Kennea (PSU), P. T. O'Brien (U Leicester),\nK. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of\nthe Swift Team:\n\nAt 06:33:46 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 170912B (trigger=772052).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 215.466, -62.030 which is \n   RA(J2000) = 14h 21m 52s\n   Dec(J2000) = -62d 01' 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 20 sec.  The peak count rate\nwas ~9500 counts/sec (15-350 keV), at ~3 sec after the trigger. \n\nThe XRT began observing the field at 06:34:36.9 UT, 50.3 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nuncatalogued X-ray source located at RA, Dec 215.45921, -61.99674 which\nis equivalent to:\n   RA(J2000)  = 14h 21m 50.21s\n   Dec(J2000) = -61d 59' 48.3\"\nwith an uncertainty of 3.6 arcseconds (radius, 90% containment). This\nlocation is 120 arcseconds from the BAT onboard position, within the\nBAT error circle. This position may be improved as more data are\nreceived; the latest position is available at\nhttp://www.swift.ac.uk/sper. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata does not constrain the column density. \n\nThe initial flux in the 2.5 s image was 4.76e-10 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 58 seconds after the BAT trigger. No credible afterglow candidate has\nbeen found in the initial data products. The 2.7'x2.7' sub-image covers 100% of\nthe XRT error circle. Because of the density of catalogued stars, further\nanalysis is required to report an upper limit for any afterglow in the\nsub-image. The 8'x8' region for the list of sources generated on-board covers\n100% of the XRT error circle. Because of the density of catalogued stars,\nfurther analysis is required to report an upper limit for any afterglow in the\nregion. No correction has been made for the large, but uncertain extinction\nexpected. \n\nBurst Advocate for this burst is S. J. LaPorte (extragsam 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": 21864,
  "createdOn": 1505198878000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 170912B: Swift detection of a burst",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 170912B"
}