TITLE: GCN CIRCULAR NUMBER: 13661 SUBJECT: GRB 120817A: Swift detection of a burst DATE: 12/08/17 06:58:40 GMT FROM: David Palmer at LANL B.P. Gompertz (U Leicester), P. A. Evans (U Leicester), C. Guidorzi (U Ferrara), K. L. Page (U Leicester), D. M. Palmer (LANL) and R. L. C. Starling (U Leicester) report on behalf of the Swift Team: At 06:49:42 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 120817A (trigger=531267). Swift could not immediately slew due to an Earth limb pointing constraint. The BAT on-board calculated location is RA, Dec 250.706, -38.340 which is RA(J2000) = 16h 42m 49s Dec(J2000) = -38d 20' 25" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multiple-peaked structure with a duration of about 25 sec. The peak count rate was ~1700 counts/sec (15-350 keV), at ~0 sec after the trigger. Due to an observing constraint, Swift will not slew until T0+50.1 minutes. There will be no XRT or UVOT data until this time. Burst Advocate for this burst is B.P. Gompertz (bpg6 AT le.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/too.html.)