[vsnet-grb-info 6545] Swift trigger 322590: BAT detection of a possible burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8153
SUBJECT: Swift trigger 322590: BAT detection of a possible burst
DATE:    08/08/28 08:50:57 GMT
FROM:    Wayne Baumgartner at GSFC  <wayne at milkyway.gsfc.nasa.gov>

W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
O. Godet (U Leicester), C. Guidorzi (INAF-OAB),
S. D. Hunsberger (PSU), V. Mangano (INAF-IASFPA), J. Mao (INAF-OAB),
C. B. Markwardt (CRESST/GSFC/UMD), P. T. O'Brien (U Leicester),
J. P. Osborne (U Leicester), K. L. Page (U Leicester),
D. M. Palmer (LANL), A. M. Parsons (GSFC), D. Perez (U Leicester),
B. Preger (ASDC), P. Romano (INAF-IASFPA), M. Stamatikos (NASA/ORAU),
R. L. C. Starling (U Leicester), G. Tagliaferri (INAF-OAB),
E. Troja (INAF-IASFPA) and T. N. Ukwatta (GSFC/GWU) report on behalf
of the Swift Team:

At 08:15:09 UT, the Swift Burst Alert Telescope (BAT) found
trigger 322590.  Swift slewed immediately to the trigger location. 
The BAT on-board calculated location is 
RA, Dec 323.467, +42.001 which is 
   RA(J2000) = 21h 33m 52s
   Dec(J2000) = +42d 00' 05"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a marginal excess,
perhaps single-peaked with a duration of about 1 sec.  The peak count rate
was ~500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 08:16:19.1 UT, 69.7 seconds after
the BAT trigger. No source was detected in 323 s of 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 224
seconds  with the V filter starting 180  seconds after the BAT
trigger. There  is a candidate afterglow in the  list of sources
generated on-board  at  
  RA(J2000)  =	21:33:45.77 = 323.4407  
  DEC(J2000) = +42:01:49.4  =  42.0304 with a 1-sigma error radius of
about 0.7 arc sec, but the DSS shows a star extremely close to this 
position. The estimated magnitude is 16.7 with a 1-sigma   error of
about 0.5 mag. No correction has been made for the expected  
extinction of about 1.7 magnitudes. 

Due to the weaknesss of the BAT detection and the lack of an 
XRT or of a reliable UVOT detection, we believe that this is not a GRB. 
However we cannot immediately rule out the possibility that this 
is a weak short burst.  Further analysis with the Malindi data
is required to determine the reality of this event. 

Burst Advocate for this burst is W. H. Baumgartner (wayne AT milkyway.gsfc.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.)