TITLE: GCN CIRCULAR NUMBER: 13762 SUBJECT: GRB 120913A: Swift detection of a burst DATE: 12/09/13 20:27:23 GMT FROM: Scott Barthelmy at NASA/GSFC E. A. Helder (PSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), N. Gehrels (NASA/GSFC), C. Gronwall (PSU), D. Grupe (PSU), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), C. B. Markwardt (NASA/GSFC), D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU) and B.-B. Zhang (PSU) report on behalf of the Swift Team: At 20:18:21 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 120913A (trigger=533568). Swift did not slew because of the Sun observing constraint. The BAT on-board calculated location is RA, Dec 146.437, +26.977 which is RA(J2000) = 09h 45m 45s Dec(J2000) = +26d 58' 36" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows several peaks with a total duration of at least 40 sec. (At T+30s, Swift executed a pre-planned slew that moved the GRB outside of the BAT FOV) The peak count rate was ~2600 counts/sec (15-350 keV), at ~23 sec after the trigger. Due to a Sun observing constraint, Swift cannot slew to the BAT position until 22:34 UT on 2012 September 27. There will thus be no XRT or UVOT data for this trigger before this time. Burst Advocate for this burst is E. A. Helder (helder AT 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.)