{
  "bibcode": "2018GCN.23158....1T",
  "body": "A. Tohuvavohu (PSU), J.D. Gropp (PSU), J. A. Kennea (PSU),\nH. A. Krimm (NSF/USRA), F. E. Marshall (NASA/GSFC),\nK. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (PSU),\nM. H. Siegel (PSU) and K. K. Simpson (PSU) report on behalf of the\nNeil Gehrels Swift Observatory Team:\n\nAt 16:40:34 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 180821A (trigger=854578).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 7.763, -38.619 which is \n   RA(J2000) = 00h 31m 03s\n   Dec(J2000) = -38d 37' 07\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  As is usual for an image trigger, the\nimmediately-available BAT lightcurve shows no obvious variation. \n\nThe XRT began observing the field at 16:44:04.8 UT, 210.3 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nfading, uncatalogued X-ray source located at RA, Dec 7.78833, -38.62660\nwhich is equivalent to:\n   RA(J2000)  = 00h 31m 09.20s\n   Dec(J2000) = -38d 37' 35.8\"\nwith an uncertainty of 3.7 arcseconds (radius, 90% containment). This\nlocation is 76 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. 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 3.67e-10 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 218 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\n0.02. \n\nBurst Advocate for this burst is A. Tohuvavohu (aaronb AT swift.psu.edu). \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": 23158,
  "createdOn": 1534870408000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 180821A: Swift detection of a burst",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 180821A"
}