{
  "bibcode": "2018GCN.23570....1M",
  "body": "M. J. Moss (George Washington University), S. D. Barthelmy (GSFC),\nA. D'Ai (INAF-IASFPA), V. D'Elia (SSDC), J. A. Kennea (PSU),\nA. Y. Lien (GSFC/UMBC) and A. Tohuvavohu (PSU) report on behalf of the\nNeil Gehrels Swift Observatory Team:\n\nAt 02:53:17 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 181228A (trigger=879909).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 49.831, +13.195, which is \n   RA(J2000)  =  03h 19m 19s\n   Dec(J2000) = +13d 11' 42\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve shows multiple overlapping peaks\nwith a duration of about 25 sec.  The peak count rate\nwas ~7000 counts/sec (15-350 keV), at ~13 sec after the trigger. \n\nThe XRT began observing the field at 02:54:40.1 UT, 82.5 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nuncatalogued X-ray source with an enhanced position: RA, Dec 49.8114,\n13.2000 which is equivalent to:\n   RA(J2000)  = 03h 19m 14.75s\n   Dec(J2000) = +13d 12' 00.1\"\nwith an uncertainty of 2.6 arcseconds (radius, 90% containment). This\nlocation is 71 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\nThe initial flux in the 2.5 s image was 5.46e-10 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of nominal 150.000 seconds with the White\nfilter starting 93 seconds after the BAT trigger. No credible afterglow\ncandidate has been found in the initial data products. Data from the 2.7'x2.7'\nsub-image are not available at this time. The 8'x8' region for the list of\nsources generated on-board covers 100% of the XRT error circle. The list of\nsources is typically complete to about 18 mag. No correction has been made for\nthe expected extinction corresponding to E(B-V) of 0.51. \n\nBurst Advocate for this burst is M. J. Moss (mikejmoss3 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": 23570,
  "createdOn": 1545966458000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "GRB 181228A: Swift detection of a burst",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 181228A"
}