TITLE: GCN CIRCULAR NUMBER: 26101 SUBJECT: GRB 191031A: Swift detection of a burst DATE: 19/10/31 00:45:49 GMT FROM: David Palmer at LANL A. D'Ai (INAF-IASFPA), E. Ambrosi (INAF-IASFPA), V. D'Elia (SSDC), J. A. Kennea (PSU), N. J. Klingler (PSU), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team: At 00:36:33 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 191031A (trigger=932435). Swift did not slew due to an observing constraint. The BAT on-board calculated location is RA, Dec 233.470, +6.144 which is RA(J2000) = 15h 33m 53s Dec(J2000) = +06d 08' 37" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 50 sec. The peak count rate was ~1500 counts/sec (15-350 keV), at ~2 sec after the trigger. Due to a Sun observing constraint, Swift cannot slew to the BAT position until 23:18 UT on 2019 December 22. There will thus be no XRT or UVOT data for this trigger before this time. Burst Advocate for this burst is A. D'Ai (antonino.dai AT inaf.it). 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/)