[vsnet-grb-info 21017] Swift Trigger 852625: a possible GRB

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23115
SUBJECT: Swift Trigger 852625: a possible GRB
DATE:    18/08/10 10:32:49 GMT
FROM:    Michael Moss at George Washington U  <mikejmoss3 at gmail.com>

M. J. Moss (George Washington University), S. D. Barthelmy (GSFC),
A. D'Ai (INAF-IASFPA), V. D'Elia (ASDC), J.D. Gropp (PSU),
A. Y. Lien (GSFC/UMBC) and F. E. Marshall (NASA/GSFC) report on behalf
of the Neil Gehrels Swift Observatory Team:

At 10:11:22 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a marginal image peak with significance of 7.07 sigma.  
Swift slewed immediately to the location. 
The BAT on-board calculated location is 
RA, Dec 144.436, -42.767 which is 
   RA(J2000) = 09h 37m 45s
   Dec(J2000) = -42d 46' 00"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual with an image trigger, the available
BAT light curve shows no significant structure. 

The XRT began observing the field at 10:13:53.1 UT, 150.5 seconds after
the BAT trigger. No source was detected in 534 s of promptly downlinked
data, which covered 96% of the BAT error circle. We are waiting for the
full dataset to detect and localise the XRT counterpart. 

UVOT took a finding chart exposure of nominal 150 seconds with the 
White filter starting 153 seconds after the BAT trigger. No credible  
afterglow candidate has been found in the initial data products.  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 0.52. 

The marginal significance of the original BAT 
image peak (7.07 sigma), and the lack of an XRT counterpart,
leads us to believe that this might be a statistical fluctuation in
the original image and not an astrophysical source. 
We need to wait for the ground data to confirm the nature of 
this source. 

Burst Advocate for this burst is M. J. Moss (mikejmoss3 AT gmail.com). 
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.)