{
  "bibcode": "2017GCN.20846....1C",
  "body": "J. R. Cummings (NASA/UMBC), K. L. Page (U Leicester),\nD. M. Palmer (LANL) and B. Sbarufatti (INAF-OAB/PSU) report on behalf\nof the Swift Team:\n\nAt 08:08:42 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 170311A (trigger=741965).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 280.563, -30.063 which is \n   RA(J2000) = 18h 42m 15s\n   Dec(J2000) = -30d 03' 45\"\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 15 sec.  The peak count rate\nwas ~1200 counts/sec (15-350 keV), at ~2 sec after the trigger. \n\nThe XRT began observing the field at 08:10:28.0 UT, 105.1 seconds after\nthe BAT trigger. Using promptly downlinked data we find a fading,\nuncatalogued X-ray source with an enhanced position: RA, Dec 280.5893,\n-30.0458 which is equivalent to:\n   RA(J2000)  = 18h 42m 21.43s\n   Dec(J2000) = -30d 02' 44.8\"\nwith an uncertainty of 2.1 arcseconds (radius, 90% containment). This\nlocation is 102 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 1.30\nx 10^21 cm^-2 (Willingale et al. 2013). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 109 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 none of\nthe XRT error circle. The 8'x8' region for the list of sources generated\non-board covers 100% of the XRT error circle. Because of the density of\ncatalogued stars, further analysis is required to report an upper limit for any\nafterglow in the region. No correction has been made for the expected\nextinction corresponding to E(B-V) of 0.16. \n\nBurst Advocate for this burst is J. R. Cummings (jayc AT milkyway.gsfc.nasa.gov). \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": 20846,
  "createdOn": 1489220714000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 170311A: Swift detection of a burst",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 170311A"
}