TITLE:   GCN CIRCULAR
NUMBER:  11274
SUBJECT: Swift BAT Trigger 433953 probably not a GRB
DATE:    10/09/12 05:11:47 GMT
FROM:    Dirk Grupe at PSU/Swift-XRT  <grupe@astro.psu.edu>

D. Grupe (PSU), S. D. Barthelmy (GSFC), M. M. Chester (PSU),
J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC),
J. M. Gelbord (PSU), C. Guidorzi (U Ferrara),
C. B. Markwardt (NASA/GSFC) and M. H. Siegel (PSU) report on behalf of
the Swift Team:

At 04:49:05 UT, the Swift Burst Alert Telescope (BAT) triggered and
located trigger 433953.  Swift slewed immediately to the location.
The BAT on-board calculated location is RA, Dec 42.643, -2.200 which is
    RA(J2000) = 02h 50m 34s
    Dec(J2000) = -02d 12' 00"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty).  The raw BAT light curve does not show an
obvious signal, which is typical for a BAT image-only trigger. The
reported image significance was 7.3.  To fully assess the significance
of the trigger we will need to examine the event-by-event data
available on the next downlink.

The XRT began observing the field at 04:51:34.5 UT, 148.7 seconds after
the BAT trigger. No source was detected in the promptly available XRT
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 151 seconds after the BAT trigger. No credible afterglow  
candidate has
been found in the initial data products. Because part of the 2.7'x2.7'
sub-image was not received, the overlap with the BAT error circle is  
uncertain.
The overlap is at most 25%. 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 0.06.