{
  "bibcode": "2017GCN.20885....1L",
  "body": "S. J. LaPorte (PSU), A. P. Beardmore (U Leicester),\nB. Mingo (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL),\nB. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf\nof the Swift Team:\n\nAt 09:45:59 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 170317A (trigger=742866).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 93.088, +50.520 which is \n   RA(J2000) = 06h 12m 21s\n   Dec(J2000) = +50d 31' 13\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a FRED\nstructure with a duration of about 10 sec.  The peak count rate\nwas ~3000 counts/sec (15-350 keV), at ~2 sec after the trigger. \n\nThe XRT began observing the field at 09:47:22.4 UT, 83.3 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source located at RA, Dec 93.06317, 50.49431 which is equivalent\nto:\n   RA(J2000)  = 06h 12m 15.16s\n   Dec(J2000) = +50d 29' 39.5\"\nwith an uncertainty of 3.6 arcseconds (radius, 90% containment). This\nlocation is 109 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 gives a column density consistent with the Galactic value of 2.53\nx 10^21 cm^-2 (Willingale et al. 2013). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 86 seconds after the BAT trigger. There is a candidate afterglow in\nthe list of sources generated on-board at\n  RA(J2000)  =\t06:12:14.78 =  93.06160\n  DEC(J2000) = +50:29:34.8  =  50.49300\nwith a 90%-confidence error radius of about 1.10 arc sec. This position is 5.7\narc sec. from the center of the XRT error circle. The estimated magnitude is\n18.05. No correction has been made for the expected extinction corresponding to\nE(B-V) of 0.19. \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": 20885,
  "createdOn": 1489744915000,
  "email": "klp5@leicester.ac.uk",
  "subject": "GRB 170317A: Swift detection of a burst with an optical counterpart",
  "submitter": "Kim Page at U.of Leicester  <klp5@leicester.ac.uk>",
  "eventId": "GRB 170317A"
}