{
  "circularId": 34938,
  "createdOn": 1699065298868,
  "subject": "GRB 231104A: Swift detection of a bright burst",
  "bibcode": "2023GCN.34938....1P",
  "body": "\nK. L. Page (U Leicester), J.D. Gropp (PSU), D. M. Palmer (LANL) and\nM. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift\nObservatory Team:\n\nAt 01:47:39 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 231104A (trigger=1194500).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 23.789, +83.791 which is \n   RA(J2000) = 01h 35m 09s\n   Dec(J2000) = +83d 47' 27\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The available BAT light curve (up to T+8s)\nshowed a complex structure with a duration of at least 12 sec. \nThe peak count rate was ~50,000 counts/sec (15-350 keV), \nat ~0 sec after the trigger. \n\nThe XRT began observing the field at 01:49:10 UT, 90.2 seconds after\nthe BAT trigger. Using promptly downlinked data we find an\nuncatalogued X-ray source with an enhanced position: RA, Dec 23.8113,\n83.7912 which is equivalent to:\n   RA(J2000)  = 01h 35m 14.7s\n   Dec(J2000) = +83d 47' 28\"\nwith an uncertainty of 3.8 arcseconds (radius, 90% containment). This\nlocation is 9 arcseconds from the BAT onboard position. This position\nmay be improved as more data are received; the latest position is\navailable at https://www.swift.ac.uk/sper. \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 860 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 25% of\nthe BAT 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\nBAT 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\n0.157. \n\nBurst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk). \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/)\n\n",
  "submitter": "David Palmer at LANL <palmer@lanl.gov>",
  "eventId": "GRB 231104A",
  "submittedHow": "email"
}