GCN Circular 16413

P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
K. L. Page (U Leicester) and M. H. Siegel (PSU) report on behalf of
the Swift Team:

At 06:37:31 UT, the Swift Burst Alert Telescope (BAT) triggered 
on a possible source (trigger=601928). Swift slewed immediately to the event. 
The BAT on-board calculated location is 
RA, Dec 324.790, +56.953 which is 
   RA(J2000) = 21h 39m 10s
   Dec(J2000) = +56d 57' 12"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  This is a very long image trigger with duration 
of 1088 s. As is usual with an image trigger, the available
BAT light curve shows no significant structure. 

The XRT began observing the field at 06:59:41.9 UT, 1330.1 seconds
after the BAT trigger. XRT found a bright X-ray source located at RA,
Dec 324.8792, 56.9866 which is equivalent to:
   RA(J2000)  = +21h 39m 31.01s
   Dec(J2000) = +56d 59' 11.8"
with an uncertainty of 6.1 arcseconds (radius, 90% containment). This
location is 212 arcseconds from the BAT onboard position. This position
is 3.0 arcseconds from  V490 Cep, a high mass X-ray binary, however it is
more than 2-sigma away from the BAT position, and so possibly unrelated to
the trigger. No event data are yet available to determine the column
density using X-ray spectroscopy. 

The initial flux in the 2.5 s image was 6.00e-10 erg cm^-2 s^-1 (0.2-10
keV). 

Because XRT centroided on the high mass X-ray binary V490 Cep, it is
likely that this object is in outburst, and it is this which triggered
the BAT. However we cannot rule out the possibility that BAT triggered
on a GRB coincidentally close to V490 Cep on the sky. 

Burst Advocate for this burst is P. A. Evans (pae9 AT star.le.ac.uk). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)