GCN Circular 43387

R. Gupta (NASA GSFC), A. Y. Lien (U Tampa), K. L. Page (U Leicester),
D. M. Palmer (LANL), C. Salvaggio (INAF-OAB) and
B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 10:14:06 UT, the Swift Burst Alert Telescope (BAT) triggered and
located an event (trigger=1439093).  Swift slewed immediately to the location.
The BAT on-board calculated location is 
RA, Dec 357.372, +9.041 which is 
   RA(J2000) = 23h 49m 29s
   Dec(J2000) = +09d 02' 29"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  We only have limited BAT light curve information 
at this moment, current light curve showed some potential pulse-like structure
in the low energy band (15-25 keV), but nothing significant in other energy bands. 
Therefore, the pulse-like structure may be due to noisy detectors. 
Further ground analysis is required to determine the nature of this trigger.

The XRT began observing the field at 10:16:22.6 UT, 136.1 seconds after
the BAT trigger. No source was detected in 1.5 ks of promptly
downlinked data.

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
0.098.

Due to the marginal detection of this event in the BAT Image (6.5 sigma)
and the lack of the an XRT counterpart detection, we believe that
this trigger is most likely to be a statistical fluctuation in the
instrument and not a true astrophysical event. Determination of the reality
of this event will require the full downlinked dataset. We retain the
name GRB 260113A for this event to avoid confusion.

Burst Advocate for this burst is R. Gupta (rahulbhu.c157 AT gmail.com).
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/)