GCN Circular 37043

M. A. Williams (PSU), S. Dichiara (PSU), R. Gupta (NASA GSFC),
J. A. Kennea (PSU) and D. M. Palmer (LANL) report on behalf of the
Neil Gehrels Swift Observatory Team:

At 14:28:54 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 240805B (trigger=1246989).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 254.239, +18.323 which is 
   RA(J2000) = 16h 56m 57s
   Dec(J2000) = +18d 19' 24"
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 70 sec.  The peak count rate
was ~2800 counts/sec (15-350 keV), at ~16 sec after the trigger. 

The XRT began observing the field at 14:30:12.5 UT, 78.4 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 254.2153, 18.3175 which is equivalent to:
   RA(J2000)  = 16h 56m 51.67s
   Dec(J2000) = +18d 19' 03.0"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This
location is 83 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 150 seconds with the White filter
starting 87 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. 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
0.087. 

Burst Advocate for this burst is M. A. Williams (mjw6837 AT psu.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/)