GCN Circular 9615

T. N. Ukwatta (GSFC/GWU), S. D. Barthelmy (GSFC), V. D'Elia (ASDC),
E. A. Hoversten (PSU), J. A. Kennea (PSU),
C. B. Markwardt (CRESST/GSFC/UMD), C. Pagani (PSU),
D. M. Palmer (LANL), M. Perri (ASDC), T. Sakamoto (NASA/UMBC),
M. H. Siegel (PSU), M. A. Stark (PSU) and G. Stratta (ASDC) report on
behalf of the Swift Team:

At 05:11:31 UT, the Swift Burst Alert Telescope (BAT) triggered and
located possible GRB 090705 (trigger=356516).  Swift slewed almost 
immediately to the location.  The BAT on-board calculated location is 
RA, Dec 318.484, +62.578 which is 
   RA(J2000) = 21h 13m 56s
   Dec(J2000) = +62d 34' 42"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual for an image trigger, there is
no obvious variation in the immediately available light curve. 

The XRT began observing the field at 05:17:25.8 UT, 354.7 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 357 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
0.83. 

Due to the marginal detection (7.02 sigma) in the BAT image, and
the non-detection by XRT, we cannot confirm that this is a real burst. 
Further analysis will require the full downlink of data through
the Malindi ground station. 

Burst Advocate for this burst is T. N. Ukwatta (tilan.ukwatta 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.)