{
  "bibcode": "2019GCN.25427....1D",
  "body": "A. D'Ai (INAF-IASFPA), E. Ambrosi (INAF-IASFPA), V. D'Elia (SSDC),\nJ.D. Gropp (PSU), J. A. Kennea (PSU), N. J. Klingler (PSU),\nH. A. Krimm (NSF), S. J. LaPorte (PSU), A. Y. Lien (GSFC/UMBC),\nF. E. Marshall (NASA/GSFC), M. J. Moss (GWU),\nK. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (PSU),\nK. K. Simpson (PSU) and A. Tohuvavohu (PSU) report on behalf of the\nNeil Gehrels Swift Observatory Team:\n\nAt 17:10:03 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 190821A (trigger=921722).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 250.077, -34.022 which is \n   RA(J2000) = 16h 40m 18s\n   Dec(J2000) = -34d 01' 16\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a multi-peaked\nstructure with a duration of about 100 sec.  The peak count rate\nwas ~2200 counts/sec (15-350 keV), at ~30 sec after the trigger. \n\nThe XRT began observing the field at 17:11:21.8 UT, 78.0 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nuncatalogued X-ray source located at RA, Dec 250.05464, -34.00719 which\nis equivalent to:\n   RA(J2000)  = 16h 40m 13.11s\n   Dec(J2000) = -34d 00' 25.9\"\nwith an uncertainty of 3.6 arcseconds (radius, 90% containment). This\nlocation is 85 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. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density in excess of the Galactic value (3.35 x\n10^21 cm^-2, Willingale et al. 2013), with an excess column of 3.2\n(+2.68/-2.37) x 10^21 cm^-2 (90% confidence). \n\nThe initial flux in the 2.5 s image was 2.95e-09 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 88 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. Because of the density of catalogued stars, further\nanalysis is required to report an upper limit for any afterglow in the\nsub-image. The 8'x8' region for the list of sources generated on-board covers\n100% of the XRT error circle. Because of the density of catalogued stars,\nfurther analysis is required to report an upper limit for any afterglow in the\nregion. No correction has been made for the expected extinction corresponding\nto E(B-V) of 0.54. \n\nBurst Advocate for this burst is A. D'Ai (antonino.dai AT inaf.it). \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/)",
  "circularId": 25427,
  "createdOn": 1566408660000,
  "email": "amy.y.lien@nasa.gov",
  "subject": "GRB 190821A: Swift detection of a burst",
  "submitter": "Amy Lien at GSFC  <amy.y.lien@nasa.gov>",
  "eventId": "GRB 190821A"
}