TITLE: GCN CIRCULAR NUMBER: 35269 SUBJECT: GRB 231205B: Swift detection of a burst DATE: 23/12/05 17:11:16 GMT FROM: K.L. Page at U Leicester <klp5@leicester.ac.uk> P. A. Evans (U Leicester), S. Dichiara (PSU), N. J. Klingler (GSFC/UMBC/CRESSTII), K. L. Page (U Leicester), D. M. Palmer (LANL), T. M. Parsotan (GSFC/UMBC/CRESSTII) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 16:43:59 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 231205B (trigger=1200812). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 54.154, +27.146 which is RA(J2000) = 03h 36m 37s Dec(J2000) = +27d 08' 47" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 40 sec. However there may be activity before the start of the immediately-available data, as the burst occurred during a pre-planned slew. The peak count rate was ~6000 counts/sec (15-350 keV), at T-3, before the nominal trigger time. The XRT began observing the field at 16:47:54.0 UT, 234.5 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 54.14912, 27.14099 which is equivalent to: RA(J2000) = 03h 36m 35.79s Dec(J2000) = +27d 08' 27.6" with an uncertainty of 3.5 arcseconds (radius, 90% containment). This location is 23 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. No spectrum from the promptly downlinked event data is yet available to determine the column density. UVOT took a finding chart exposure starting 237 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. Burst Advocate for this burst is P. A. Evans (pae9 AT leicester.ac.uk). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/35269. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...