GCN Circular 29970

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/)