{
  "bibcode": "2018GCN.22573....1L",
  "body": "A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), A. Deich (PSU),\nJ.D. Gropp (PSU), J. A. Kennea (PSU), K. L. Page (U Leicester) and\nA. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift\nObservatory Team:\n\nAt 15:38:39 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 180331B (trigger=820513).  Swift executed a delayed slewed\ndue to an observing constraint.  The BAT on-board calculated location is \nRA, Dec 196.820, +61.725, which is \n   RA(J2000)  =  13h 07m 17s\n   Dec(J2000) = +61d 43' 30\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve shows a single peak\nwith a duration of about 8 sec.  The peak count rate\nwas ~1500 counts/sec (15-350 keV), at ~2 sec after the trigger. \n\nThe XRT began observing the field at 15:49:43.0 UT, 663.7 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source with an enhanced position: RA, Dec 196.7829, 61.7271 which\nis equivalent to:\n   RA(J2000)  = 13h 07m 07.91s\n   Dec(J2000) = +61d 43' 37.5\"\nwith an uncertainty of 2.4 arcseconds (radius, 90% containment). This\nlocation is 63 arcseconds from the BAT onboard position, within the BAT\nerror circle. This position may be improved as more data are received;\nthe latest position is available at http://www.swift.ac.uk/sper.  We\ncannot determine whether the source is fading at the present time. No\nspectrum from the promptly downlinked event data is yet available to\ndetermine the column density. \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 667 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. 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 A. Y. Lien (amy.y.lien AT 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": 22573,
  "createdOn": 1522511931000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "GRB 180331B: Swift detection of a burst",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 180331B"
}