TITLE: GCN CIRCULAR NUMBER: 25176 SUBJECT: GRB 190727B: Swift detection of a burst DATE: 19/07/27 20:28:15 GMT FROM: David Palmer at LANL A. Y. Lien (GSFC/UMBC), M. G. Bernardini (INAF-OAB), P. D'Avanzo (INAF-OAB), J. A. Kennea (PSU), N. J. Klingler (PSU), A. Melandri (INAF-OAB), M. J. Moss (GWU), K. L. Page (U Leicester), D. M. Palmer (LANL) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 20:18:17 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 190727B (trigger=916733). Swift could not slew to the location due to an observing constraint. The BAT on-board calculated location is RA, Dec 126.481, -13.268 which is RA(J2000) = 08h 25m 55s Dec(J2000) = -13d 16' 03" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 50 sec. The peak count rate was ~20,000 counts/sec (15-350 keV), at ~1 sec after the trigger. Due to a Sun observing constraint, Swift cannot slew to the BAT position until 16:42 UT on 2019 September 12. There will thus be no XRT or UVOT data for this trigger before this time. Burst Advocate for this burst is A. Y. Lien (amy.y.lien 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/)