[vsnet-grb-info 9223] Trigger 421072: Possible Swift detection of a GRB or transient

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10708
SUBJECT: Trigger 421072: Possible Swift detection of a GRB or transient
DATE:    10/05/04 07:56:22 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

C. Pagani (U Leicester), A. P. Beardmore (U Leicester),
S. Campana (INAF-OAB), P. A. Evans (U Leicester),
C. Guidorzi (U Ferrara), O. M. Littlejohns (U Leicester),
C. B. Markwardt (CRESST/GSFC/UMD), P. T. O'Brien (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL),
A. Rowlinson (U Leicester), M. Stamatikos (OSU/NASA/GSFC),
M. A. Stark (PSU), R. L. C. Starling (U Leicester) and
G. Tagliaferri (INAF-OAB) report on behalf of the Swift Team:

At 07:28:34 UT, the Swift Burst Alert Telescope (BAT) 
located trigger 421072.  Swift slewed immediately to the location. 
The BAT on-board calculated location is RA, Dec 98.246, +9.165 which is 
   RA(J2000) = 06h 32m 59s
   Dec(J2000) = +09d 09' 55"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  Because the BAT trigger is based on a 64 s
image in the 15-50 keV band, there is nothing obvious in the light curve,
which is typical.  In ground processing, the excess has a significance of
6.4 sigma. 

The XRT began observing the field at 07:30:31.7 UT, 117.5 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 121 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.  Data from the list of
sources generated on-board are not available at this  time. No
correction has been made for the large, but uncertain extinction 
expected. 

Due to the low significance (6.4 sigma) of this source in the
ground reprocessing of the BAT image, and the lack of confirmation 
by XRT and UVOT, we cannot confirm that this is an astrophysical
source.  Furthermore its proximity to the Galactic plane (7 arcmin)
would suggest the possibility of it being a Galactic transient if
it were real.  Therefore further determination of the reality
and nature of this source will require analysis of the Malindi data. 

Burst Advocate for this burst is C. Pagani (cp232 AT star.le.ac.uk). 
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.)