TITLE: GCN CIRCULAR NUMBER: 23383 SUBJECT: GRB 181027A: Swift detection of a burst DATE: 18/10/27 01:57:37 GMT FROM: David Palmer at LANL A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester), D. M. Palmer (LANL) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 01:48:59 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 181027A (trigger=868984). Swift could not slew to the burst due to an observing constraint. The BAT on-board calculated location is RA, Dec 225.383, +30.891 which is RA(J2000) = 15h 01m 32s Dec(J2000) = +30d 53' 28" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 80 sec. The peak count rate was ~1200 counts/sec (15-350 keV), at ~49 sec after the trigger. Due to a Sun observing constraint, Swift cannot slew to the BAT position until 03:50 UT on 2018 November 06. There will thus be no XRT or UVOT data for this trigger before this time. Burst Advocate for this burst is A. Y. Lien (amy.y.lien AT nasa.gov). 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/too.html.)