{
  "bibcode": "2022GCN.32774....1P",
  "body": "K. L. Page (U Leicester), J. A. Kennea (PSU),\nN. J. Klingler (GSFC/UMBC/CRESSTII), A. Y. Lien (U Tampa),\nF. E. Marshall (NASA/GSFC), D. M. Palmer (LANL),\nA. Tohuvavohu (U Toronto) and M. A. Williams (PSU) report on behalf of\nthe Neil Gehrels Swift Observatory Team:\n\nAt 23:39:24 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 221016A (trigger=1129775).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 38.949, -34.624 which is \n   RA(J2000) = 02h 35m 48s\n   Dec(J2000) = -34d 37' 26\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a single peak\nwith tail structure with a duration of about 30 sec.  The peak count rate\nwas ~3500 counts/sec (15-350 keV), at ~0 sec after the trigger. \n\nThe XRT began observing the field at 23:42:24.0 UT, 179.8 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source located at RA, Dec 38.94479, -34.61039 which is equivalent\nto:\n   RA(J2000)  = 02h 35m 46.75s\n   Dec(J2000) = -34d 36' 37.4\"\nwith an uncertainty of 3.7 arcseconds (radius, 90% containment). This\nlocation is 50 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 https://www.swift.ac.uk/sper.  We\ncannot determine whether the source is fading at the present time. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density in excess of the Galactic value (3.53 x\n10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.8\n(+3.14/-2.70) x 10^21 cm^-2 (90% confidence). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 97 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 none of\nthe XRT error circle. The 8'x8' region for the list of sources generated\non-board covers 100% of the XRT error circle. The list of sources is typically\ncomplete to about 18 mag. No correction has been made for the expected\nextinction corresponding to E(B-V) of 0.026. \n\nBurst Advocate for this burst is K. L. Page (kimlpage1978 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/)",
  "circularId": 32774,
  "createdOn": 1665964402000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 221016A: Swift detection of a burst",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 221016A"
}