GCN Circular 36931

K. L. Page (U Leicester), D. M. Palmer (LANL),
B. Sbarufatti (INAF-OAB) and M. H. Siegel (PSU) report on behalf of
the Neil Gehrels Swift Observatory Team:

At 02:37:36 UT, the Swift Burst Alert Telescope (BAT) triggered on
a rate fluctuation at the 0.032 s timescale and found a low-significance
peak in the resulting image (trigger=1244778). 
Swift slewed immediately to the location. 
The BAT on-board calculated location is 
RA, Dec 299.054, -64.667 which is 
   RA(J2000) = 19h 56m 13s
   Dec(J2000) = -64d 40' 00"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve does not show any
obvious peak above the noise level. 

The XRT began observing the field at 02:39:04.6 UT, 87.7 seconds after
the BAT trigger. No source was detected in 674 s of promptly downlinked
data. 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
303 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 19.2 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 18.0 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.068. 

Due to the marginal signal in the BAT (6.7 sigma in rates, 6.7 sigma
in the image) and the lack of an XRT or UVOT counterpart, we believe
that this is merely a statistical fluctuation in the BAT image
reconstruction and not an astrophysical event.  This conclusion
is expected to be confirmed when the full dataset is available
on the ground.