GCN Circular 36493

T. M. Parsotan (GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL)
and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels
Swift Observatory Team:

At 03:36:28 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 240516A (trigger=1228797).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 212.770, -63.505 which is 
   RA(J2000) = 14h 11m 05s
   Dec(J2000) = -63d 30' 17"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of at least 20 sec.  The peak count rate
was ~1400 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 03:38:50.4 UT, 142.1 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 212.8071, -63.4878 which is equivalent to:
   RA(J2000)  = 14h 11m 13.70s
   Dec(J2000) = -63d 29' 16.1"
with an uncertainty of 6.1 arcseconds (radius, 90% containment). This
location is 85 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

UVOT took a finding chart exposure of	2 seconds with the White filter
starting 150 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. Because of the density of catalogued stars, further
analysis is required to report an upper limit for any afterglow in the
sub-image. Results from the list of sources generated on-board are not
available at this time. No correction has been made for the large, but
uncertain, extinction expected. 

Burst Advocate for this burst is T. M. Parsotan (parsotat AT umbc.edu). 
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/)