{
  "bibcode": "2018GCN.22468....1P",
  "body": "K. L. Page (U Leicester), A. Deich (PSU), S. W. K Emery (UCL-MSSL),\nJ. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL),\nM. H. Siegel (PSU) and A. Tohuvavohu (PSU) report on behalf of the\nNeil Gehrels Swift Observatory Team:\n\nAt 18:03:49 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 180311A (trigger=813721).  Swift slewed to the burst after\na brief delay to clear the Earth limb observing contraint. \nThe BAT on-board calculated location is \nRA, Dec 3.433, -54.479 which is \n   RA(J2000) = 00h 13m 44s\n   Dec(J2000) = -54d 28' 43\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a complex peak\nstructure with a duration of about 30 sec.  The peak count rate\nwas ~1000 counts/sec (15-350 keV), at ~4 sec after the trigger. \n\nThe XRT began observing the field at 18:08:24.5 UT, 275.3 seconds after\nthe BAT trigger. Using promptly downlinked data we find a fading,\nuncatalogued X-ray source located at RA, Dec 3.39027, -54.49162 which\nis equivalent to:\n   RA(J2000)  = 00h 13m 33.66s\n   Dec(J2000) = -54d 29' 29.8\"\nwith an uncertainty of 3.7 arcseconds (radius, 90% containment). This\nlocation is 100 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 in excess of the Galactic value (1.59 x\n10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.9\n(+3.32/-2.86) x 10^21 cm^-2 (90% confidence). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 279 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 26% of\nthe XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. \nThe 8'x8' region for the list of sources generated on-board covers 100% of the\nXRT error circle. The list of sources is typically complete to about 18 mag. No\ncorrection has been made for the expected extinction corresponding to E(B-V) of\n0.01. \n\nBurst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk). \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": 22468,
  "createdOn": 1520792280000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 180311A: Swift detection of a burst",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 180311A"
}