TITLE: GCN CIRCULAR NUMBER: 23046 SUBJECT: GRB 180728A: Swift detection of a bright burst DATE: 18/07/28 17:38:09 GMT FROM: David Palmer at LANL R. L. C. Starling (U Leicester), S. D. Barthelmy (GSFC), A. Y. Lien (GSFC/UMBC), M. J. Moss (George Washington University), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team: At 17:29:00 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180728A (trigger=850471). Swift did not slew immediately due to the Earth limb constraint. The BAT on-board calculated location is RA, Dec 253.569, -54.031 which is RA(J2000) = 16h 54m 17s Dec(J2000) = -54d 01' 50" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a small precursor followed 10 seconds later by a bright FRED pulse of ~20 s duration. The peak count rate was ~100,000 counts/sec (15-350 keV), at ~13 sec after the trigger. Due to an observing constraint, Swift will not slew until T0+23.6 minutes. There will be no XRT or UVOT data until this time. Burst Advocate for this burst is R. L. C. Starling (rlcs1 AT star.le.ac.uk). 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.)