[vsnet-grb-info 18266] Swift Trigger 704444 is probably not an astrophysical event.

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19714
SUBJECT: Swift Trigger 704444 is probably not an astrophysical event. 
DATE:    16/07/15 01:20:16 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL) and
T. G. R. Roegiers (PSU) report on behalf of the Swift Team:

At 01:02:07 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a possible source (trigger=704444).  Swift slewed immediately 
to the location. 
The BAT on-board calculated location is 
RA, Dec 193.774, +13.145 which is 
   RA(J2000) = 12h 55m 06s
   Dec(J2000) = +13d 08' 42"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual with an image trigger, the available
BAT light curve shows no significant structure. 

The XRT began observing the field at 01:04:17.9 UT, 130.5 seconds after
the BAT trigger. No source was detected in 213 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 136 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
0.04. 

This is a low significance (5.96 sigma) peak in an image produced 
in the absence of a rate increase.  Swift slews to such marginal
detections only when they are sufficiently near a source in the
onboard catalog to allow XRT and UVOT to confirm or refute the
possible activity. 

In this case, the lack of XRT detection strongly suggests 
that this was merely a noise fluctuation in the image. 

We do not believe that this was an astrophysical event.