[vsnet-grb-info 19141] Trigger 738728: Swift triggered on noise near NGC 4096

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  20688
SUBJECT: Trigger 738728: Swift triggered on noise near NGC 4096
DATE:    17/02/16 19:39:35 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at milkyway.gsfc.nasa.gov>

S. D. Barthelmy (GSFC), S. B. Cenko (GSFC),
F. E. Marshall (NASA/GSFC), B. Mingo (U Leicester),
K. L. Page (U Leicester) and E. Troja (NASA/GSFC/UMCP) report on
behalf of the Swift Team:

At 19:21:57 UT, the Swift Burst Alert Telescope (BAT) triggered on noise
near NGC 4096 (trigger=738728).  The image significance was 5.86 sigma. 
Swift slewed immediately to the location.  The BAT on-board calculated location
is RA, Dec 181.474, +47.650, which is 
   RA(J2000)  =  12h 05m 54s
   Dec(J2000) = +47d 38' 60"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is typical for an image trigger
there is nothing significant in the real-time light curve. 

The XRT began observing the field at 19:24:12.9 UT, 135.5 seconds after
the BAT trigger. No source was detected in 411 s 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
0.02.