GCN Circular 42656

A. Mei (INAF-OAB), J. J. DeLaunay (PSU), M. Ferro (INAF-OAB),
R. Gupta (NASA GSFC) and M. H. Siegel (PSU) report on behalf of the
Neil Gehrels Swift Observatory Team:

At 21:28:56 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a possible GRB 251112A (trigger=1413695).  Swift slewed immediately to the burst.
The BAT on-board calculated location is 
RA, Dec 274.019, +24.226 which is 
   RA(J2000) = 18h 16m 05s
   Dec(J2000) = 24d 13' 32"
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 60 sec.  The peak count rate
was ~600 counts/sec (15-350 keV), at ~25 sec after the trigger.

The XRT began observing the field at 21:30:22.7 UT, 86.9 seconds after
the BAT trigger. No source was detected in 782 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 91 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
0.161.

Due to no credible afterglow candidate in the initial XRT and UVOT
data, we for now call this a possible GRB while we wait for
additional data for further inspection.

Burst Advocate for this burst is A. Mei (alessio.mei AT inaf.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/)