TITLE: GCN CIRCULAR NUMBER: 29970 SUBJECT: GRB 210509A: Swift detection of a burst DATE: 21/05/09 14:45:48 GMT FROM: David Palmer at LANL K. L. Page (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team: At 14:32:20 UT, the Swift Burst Alert Telescope (BAT) triggered and located a GRB 210509A (trigger= 1047531). Swift did not slew immediately due to an observing constraint. The BAT on-board calculated location is RA, Dec 350.352, +6.675 which is RA(J2000) = 23h 21m 25s Dec(J2000) = +06d 40' 31" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). Due to telemetry limitations, no further BAT data will be available until the ground-station pass data has been processed. Due to an observing constraint, Swift will not slew until T0+50 minutes. There will be no XRT or UVOT data until this time. Burst Advocate for this burst is K. L. Page (klp5 AT leicester.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/)