{
  "bibcode": "2020GCN.28499....1C",
  "body": "S. B. Cenko (GSFC), C. Gronwall (PSU), J.D. Gropp (PSU),\nN. J. Klingler (PSU), H. A. Krimm (NSF), A. Y. Lien (GSFC/UMBC),\nF. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),\nD. M. Palmer (LANL) and A. Tohuvavohu (U Toronto) report on behalf of\nthe Neil Gehrels Swift Observatory Team:\n\nAt 21:50:37 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 200925B (trigger=997453).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 246.851, +78.394 which is \n   RA(J2000) = 16h 27m 24s\n   Dec(J2000) = +78d 23' 39\"\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 40 sec.  The peak count rate\nwas ~2000 counts/sec (15-350 keV), at ~5 sec after the trigger. \n\nThe XRT began observing the field at 21:51:55.3 UT, 78.4 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source located at RA, Dec 246.78990, 78.39033 which is equivalent\nto:\n   RA(J2000)  = 16h 27m 09.58s\n   Dec(J2000) = +78d 23' 25.2\"\nwith an uncertainty of 3.9 arcseconds (radius, 90% containment). This\nlocation is 46 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 consistent with the Galactic value of 4.59\nx 10^20 cm^-2 (Willingale et al. 2013). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 81 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\n0.04. \n\nBurst Advocate for this burst is S. B. Cenko (brad.cenko AT nasa.gov). \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": 28499,
  "createdOn": 1601071250000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 200925B: Swift detection of a burst",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 200925B"
}