GCN Circular 13843

S. D. Barthelmy (GSFC), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU),
C. B. Markwardt (NASA/GSFC) and M. H. Siegel (PSU) report on behalf of
the Swift Team:

At 23:57:42 UT, the Swift Burst Alert Telescope (BAT) triggered and
located trigger 535733.  Swift slewed immediately to the location. 
The BAT on-board calculated location is 
RA, Dec 277.193, -10.479 which is 
   RA(J2000) = 18h 28m 46s
   Dec(J2000) = -10d 28' 42"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As typical for image triggers (64-sec), the prompt
lightcurve data shows nothing significant.  This position is marginally
consistent with the known source SAX J1828.5-1037.  We note that the 
detection significance is marginal as well. 

The XRT began observing the field at 23:59:42.7 UT, 120.5 seconds after
the BAT trigger. No source was detected in the 2.5-s promptly available
image. We are waiting for the full dataset to detect and localise the
XRT counterpart. 

UVOT took a finding chart exposure of	6 seconds with the White filter
starting 123 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. 
Results from the list of sources generated on-board are not available at this
time. No correction has been made for the large, but uncertain extinction
expected.