[vsnet-grb-info 21047] Swift Trigger 853790 is probably not an astrophysical source

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23145
SUBJECT: Swift Trigger 853790 is probably not an astrophysical source
DATE:    18/08/17 21:16:48 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

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

At 20:58:18 UT, the Swift Burst Alert Telescope (BAT) triggered on a
low significance image peak near the line of sight to a nearby 
galaxy (trigger=853790).  Swift did not slew due to an observing 
constraint.  The BAT on-board calculated location is 
RA, Dec 192.885, +25.921 which is 
   RA(J2000) = 12h 51m 32s
   Dec(J2000) = +25d 55' 15"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is typical for an image trigger, there
no obvious structure in the immediately available lightcurve. 

This position is too close to the Sun for Swift to observe until 
2018 November 02. Thus there will be no XRT or UVOT data for this 
trigger. 

Due to the low significance of the image peak (6.1 sigma on-board,
with an even lower significance in the ground analysis of the 
immediately-available detector plane data), the
lack of a rate trigger, and the offset from the putative
nearby galaxy (9 arcminutes) we believe that this is probably
just a statistical fluctuation in the image plane and not
an astrophysical source.  The complete downlinked BAT data will
be used to confirm or refute this.  There will be no XRT or UVOT
follow-up due to the observing constraint.