TITLE:   GCN CIRCULAR
NUMBER:  19226
SUBJECT: Swift Trigger 680457 is not a GRB
DATE:    16/03/25 13:47:20 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

S. D. Barthelmy (GSFC), D. N. Burrows (PSU), J. A. Kennea (PSU),
A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester),
T. G. R. Roegiers (PSU), B. Sbarufatti (INAF-OAB/PSU) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 13:16:35 UT, the Swift Burst Alert Telescope (BAT) triggered 
on a noise event (trigger=680457).  Swift slewed immediately. 
The BAT on-board calculated location is 
RA, Dec 292.702, -0.668, which is 
   RA(J2000)  =  19h 30m 48s
   Dec(J2000) = -00d 40' 02"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The real-time TDRSS BAT light curve does not show
anything significant. 

Given that this trigger occurred while entering the SAA region, the increasing
background diminishes the likelihood that this trigger is real.  That plus
the low image domain significance (6.55 sigma) indicates that this trigger
is due to noise and not anything astrophysical. 

The XRT began observing the field at 13:17:27.8 UT, 52.8 seconds after
the BAT trigger. No source was detected in the 2.5-s promptly available
image.