GCN Circular 27845

V. D'Elia (SSDC), E. Ambrosi (INAF-IASFPA), A. D'Ai (INAF-IASFPA),
J.D. Gropp (PSU), J. A. Kennea (PSU), N. J. Klingler (PSU),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC/CRESST), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), M. J. Moss (GWU), D. M. Palmer (LANL),
A. Tohuvavohu (U Toronto) and T. N. Ukwatta (LANL) report on behalf of
the Neil Gehrels Swift Observatory Team:

At 00:56:35 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 200529A (trigger=974942).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 238.751, -11.057 which is 
   RA(J2000) = 15h 55m 00s
   Dec(J2000) = -11d 03' 25"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a weak pulse
with a duration of about 30 sec.  The peak count rate
was ~1700 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 01:00:08.7 UT, 212.9 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 238.76571, -11.07215 which is
equivalent to:
   RA(J2000)  = 15h 55m 03.77s
   Dec(J2000) = -11d 04' 19.7"
with an uncertainty of 5.2 arcseconds (radius, 90% containment). This
location is 75 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at https://www.swift.ac.uk/sper. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

UVOT took a finding chart exposure of 144 seconds with the White filter
starting 216 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 56% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.29. 

Burst Advocate for this burst is V. D'Elia (delia AT ssdc.asi.it). 
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/)