TITLE: GCN CIRCULAR NUMBER: 11288 SUBJECT: GRB 100917A: Swift detection of a burst DATE: 10/09/17 05:23:07 GMT FROM: Owen Littlejohns at U of Leicester O. M. Littlejohns (U Leicester), A. P. Beardmore (U Leicester), P. A. Evans (U Leicester), J. M. Gelbord (PSU), E. A. Hoversten (PSU), C. B. Markwardt (NASA/GSFC), C. Pagani (U Leicester), K. L. Page (U Leicester), A. Rowlinson (U Leicester), M. H. Siegel (PSU) and C. A. Swenson (PSU) report on behalf of the Swift Team: At 05:03:25 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 100917A (trigger=434360). Swift did not slew to the burst location due to a moon observing constraint. The BAT on-board calculated location is RA, Dec 289.265, -17.104 which is RA(J2000) = 19h 17m 04s Dec(J2000) = -17d 06' 15" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a weak peak with a duration of about 4 sec. The peak count rate was ~400 counts/sec (15-350 keV), at ~1 sec after the trigger. Due to an observing constraint, Swift cannot slew to the BAT position. There will thus be no XRT or UVOT data for this trigger. This trigger will be in moon constraint until approximately 06:30 UT on the 19th of September. Burst Advocate for this burst is O. M. Littlejohns (oml2 AT star.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.)