TITLE: GCN CIRCULAR NUMBER: 21826 SUBJECT: GRB 170906C: Swift detection of a burst DATE: 17/09/06 07:37:56 GMT FROM: Scott Barthelmy at NASA/GSFC M. H. Siegel (PSU), S. D. Barthelmy (GSFC), P. A. Evans (U Leicester), C. Gronwall (PSU), K. L. Page (U Leicester) and A. Tohuvavohu (PSU) report on behalf of the Swift Team: At 07:26:17 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 170906C (trigger=770981). Swift did not slew due to an observing constraint. The BAT on-board calculated location is RA, Dec 128.704, +70.782, which is RA(J2000) = 08h 34m 49s Dec(J2000) = +70d 46' 54" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows multiple overlapping peaks with a total duration of about 30 sec. The peak count rate was ~4000 counts/sec (15-350 keV), at ~6 sec after the trigger. Due to an observing constraint, Swift will not slew until T0+18.9 minutes. There will be no XRT or UVOT data until this time. Burst Advocate for this burst is M. H. Siegel (siegel AT swift.psu.edu). 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.)