TITLE: GCN CIRCULAR NUMBER: 9945 SUBJECT: GRB 090927: Swift detection of a short burst DATE: 09/09/27 10:19:48 GMT FROM: David Palmer at LANL D. Grupe (PSU), J. R. Cummings (NASA/UMBC), C. Gronwall (PSU), C. Guidorzi (U Ferrara), C. B. Markwardt (CRESST/GSFC/UMD), P. T. O'Brien (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), P. Romano (INAF-IASFPA), M. H. Siegel (PSU), T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the Swift Team: At 10:07:16 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 090927 (trigger=370846). The BAT on-board calculated location is RA, Dec 343.953, -70.978 which is RA(J2000) = 22h 55m 49s Dec(J2000) = -70d 58' 38" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 1.5 sec. The peak count rate was ~4000 counts/sec (15-350 keV), at ~1 sec after the trigger. Due to an observing constraint, Swift will not slew until T0+33.8 minutes. There will be no XRT or UVOT data until this time. Burst Advocate for this burst is D. Grupe (grupe AT astro.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.)