{
  "bibcode": "2022GCN.32465....1B",
  "body": "M. G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB),\nM. Ferro (INAF-OAB), J.D. Gropp (PSU), A. Melandri (INAF-OAB),\nK. L. Page (U Leicester), D. M. Palmer (LANL),\nT. M. Parsotan (GSFC/UMBC/CRESSTII), T. Sbarrato (INAF-OAB) and\nM. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift\nObservatory Team:\n\nAt 19:23:03 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 220813A (trigger=1120270).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 81.501, -32.985 which is \n   RA(J2000) = 05h 26m 00s\n   Dec(J2000) = -32d 59' 06\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a single-peak\nstructure with a duration of about 30 sec.  The peak count rate\nwas ~1200 counts/sec (15-350 keV), at ~2 sec after the trigger. \n\nThe XRT began observing the field at 19:24:34.2 UT, 90.6 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nfading, uncatalogued X-ray source located at RA, Dec 81.53235,\n-33.01546 which is equivalent to:\n   RA(J2000)  = 05h 26m 07.76s\n   Dec(J2000) = -33d 00' 55.7\"\nwith an uncertainty of 3.7 arcseconds (radius, 90% containment). This\nlocation is 144 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\nhttps://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 (2.32 x\n10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.7\n(+3.14/-2.65) x 10^21 cm^-2 (90% confidence). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 100 seconds after the BAT trigger. There is a candidate afterglow in\nthe rapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t05:26:07.57 =  81.53155\n  DEC(J2000) = -33:00:58.9  = -33.01636\nwith a 90%-confidence error radius of about 0.67 arc sec. This position is 4.7\narc sec. from the center of the XRT error circle. The estimated magnitude is\n19.61 with a 1-sigma error of about  0.17. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.022. \n\nBurst Advocate for this burst is M. G. Bernardini (grazia.bernardini AT brera.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": 32465,
  "createdOn": 1660419348000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 220813A: Swift detection of a burst with an optical counterpart",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 220813A"
}