TITLE: GCN CIRCULAR NUMBER: 18389 SUBJECT: Swift Trigger 657564: a probable GRB DATE: 15/10/04 18:19:25 GMT FROM: Scott Barthelmy at NASA/GSFC S. B. Cenko (GSFC), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU), E. Troja (NASA/GSFC/UMCP) and T. N. Ukwatta (LANL) report on behalf of the Swift Team: At 18:09:04 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 151004A (trigger=657564). Swift did not slew due to the Earth-limb observing constraint. The BAT on-board calculated location is RA, Dec 213.585, -64.947, which is RA(J2000) = 14h 14m 20s Dec(J2000) = -64d 56' 49" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is typical for image triggers, the real-time light curve does not show anything significant. Due to an observing constraint, Swift will not slew until T0+56.9 minutes. There will be no XRT or UVOT data until this time. Burst Advocate for this burst is S. B. Cenko (brad.cenko AT 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.)