TITLE:   GCN CIRCULAR
NUMBER:  11055
SUBJECT: Trigger 430975: Swift detection of a possible burst
DATE:    10/08/05 08:27:36 GMT
FROM:    Michael Stroh at PSU/Swift  <stroh@astroh.org>

M. C. Stroh (PSU), P. A. Evans (U Leicester), J. M. Gelbord (PSU),
O. Godet (U Leicester), C. Gronwall (PSU), C. Guidorzi (U Ferrara),
S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU),
C. B. Markwardt (NASA/GSFC), P. T. O'Brien (U Leicester),
J. P. Osborne (U Leicester), K. L. Page (U Leicester) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 07:54:57 UT, the Swift Burst Alert Telescope (BAT) triggered and
located trigger=430975.  Swift slewed immediately to the location. 
The BAT on-board calculated location is RA, Dec 56.582, -3.694 which is 
   RA(J2000) = 03h 46m 20s
   Dec(J2000) = -03d 41' 37"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT trigger is a 64-sec image trigger with
significance 7.04 sigma.  The BAT light curve shows no obvious structure, 
which is typical for an image trigger.  At the present time we do not have 
BAT image data on the ground, which would allow further assessment of the
trigger quality. 

The XRT began observing the field at 07:57:13.9 UT, 135.9 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 140 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
0.14. 

Burst Advocate for this burst is M. C. Stroh (stroh AT astroh.org). 
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.)