TITLE: GCN CIRCULAR NUMBER: 10062 SUBJECT: GRB 091024: Swift detection of a burst DATE: 09/10/24 09:09:05 GMT FROM: David Palmer at LANL F. E. Marshall (NASA/GSFC), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), S. Campana (INAF-OAB), P. A. Evans (U Leicester), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), C. B. Markwardt (CRESST/GSFC/UMD), P. T. O'Brien (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), T. Sakamoto (NASA/UMBC), B. Sbarufatti (INAF-IASFPA), R. L. C. Starling (U Leicester) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team: At 08:56:01 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 091024 (trigger=373674). The BAT on-board calculated location is RA, Dec 339.207, +56.874 which is RA(J2000) = 22h 36m 50s Dec(J2000) = +56d 52' 28" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a double-peaked structure with the first peak at T=0 and a second smaller peak at T=40s with a total duration of about 50 sec. The peak count rate was ~5000 counts/sec (15-350 keV), at ~0 sec after the trigger. Due to an observing constraint, Swift will not slew until T0+50.0 minutes. There will be no XRT or UVOT data until this time. Burst Advocate for this burst is F. E. Marshall (marshall AT milkyway.gsfc.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.)