[vsnet-grb-info 18332] Swift Trigger 707517 is probably not a GRB

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19780
SUBJECT: Swift Trigger 707517 is probably not a GRB
DATE:    16/08/06 05:41:29 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

J. L. Racusin (NASA/GSFC), P. D'Avanzo (INAF-OAB), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), A. Melandri (INAF-OAB),
D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the
Swift Team:

At 05:18:31 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a marginal peak (trigger=707517).  Swift slewed
immediately to the location. 
The BAT on-board calculated location is 
RA, Dec 98.208, -22.786 which is 
   RA(J2000) = 06h 32m 50s
   Dec(J2000) = -22d 47' 08"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As with most image triggers, there is no
obvious variation in the immediately-available BAT lightcurve. 

The XRT began observing the field at 05:20:37.4 UT, 126.1 seconds after
the BAT trigger. No source was detected in 867 s of promptly downlinked
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 338 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. No correction has been made for the  expected extinction
corresponding to E(B-V) of 0.09. 

Due to the lack of a rate increase in BAT, the marginal nature of
the peak (7.15 sigma) and the lack of an XRT afterglow, we believe
that this is probably not a GRB.  A final determination will
require the complete downlinked dataset. 

Burst Advocate for this burst is J. L. Racusin (judith.racusin AT nasa.gov). 
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.)