{
  "bibcode": "2021GCN.30765....1S",
  "body": "E. Sonbas (Adiyaman Univ.), E. Ambrosi (INAF-IASFPA),\nA. D'Ai (INAF-IASFPA), V. D'Elia (SSDC & INAF-OAR), C. Gronwall (PSU),\nS. Laha (GSFC/UMBC/CRESST), A. Y. Lien (U Tampa),\nF. E. Marshall (NASA/GSFC) and D. M. Palmer (LANL) report on behalf of\nthe Neil Gehrels Swift Observatory Team:\n\nAt 00:12:41 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 210905A (trigger=1071993).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 309.062, -44.431 which is \n   RA(J2000) = 20h 36m 15s\n   Dec(J2000) = -44d 25' 50\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a complex\nstructure with a duration of at least 30 sec.  The peak count rate\nwas ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger. \n\nThe XRT began observing the field at 00:14:13.0 UT, 91.7 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nuncatalogued X-ray source located at RA, Dec 309.04815, -44.43959 which\nis equivalent to:\n   RA(J2000)  = 20h 36m 11.56s\n   Dec(J2000) = -44d 26' 22.5\"\nwith an uncertainty of 7.0 arcseconds (radius, 90% containment). This\nlocation is 47 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. 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 1.23e-09 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 250 seconds with the U filter starting\n156 seconds after the BAT trigger. No credible afterglow candidate has been\nfound in the initial data products. The 2.7'x2.7' sub-image covers 100% of the\nXRT error circle. The typical 3-sigma upper limit has been about 19.2 mag. The\n8'x8' region for the list of sources generated on-board covers 100% of the XRT\nerror circle. The list of sources is typically complete to about 18.0 mag. No\ncorrection has been made for the expected extinction corresponding to E(B-V) of\n0.034. \n\nBurst Advocate for this burst is E. Sonbas (edasonbas AT yahoo.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": 30765,
  "createdOn": 1630801709000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 210905A: Swift detection of a burst",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 210905A"
}