GCN Circular 37254

S. B. Cenko (GSFC), S. Dichiara (PSU), M. Ferro (INAF-OAB),
A. Y. Lien (U Tampa), D. M. Palmer (LANL), C. Salvaggio (INAF-OAB) and
A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 01:03:25 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 240824A (trigger=1250282).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 213.203, +63.737 which is 
   RA(J2000) = 14h 12m 49s
   Dec(J2000) = +63d 44' 13"
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 40 sec.  The peak count rate
was ~1200 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 01:05:39.6 UT, 134.2 seconds after
the BAT trigger. No source was detected in 734 s of promptly downlinked
data. We are waiting for the full dataset to detect and localise the
XRT counterpart. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 139 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 25% of
the BAT 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
BAT 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
0.014. 

Although we do not see an X-ray or optical counterpart, the high
significance of the source detection in BAT (>9 sigma, confirmed
by re-imaging on the ground) gives us confidence that this is
an astrophysical source. 

Burst Advocate for this burst is S. B. Cenko (brad.cenko AT nasa.gov). 
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/)