TITLE:   GCN CIRCULAR
NUMBER:  7912
SUBJECT: Trigger 315630: Swift detection of a possible burst
DATE:    08/07/01 13:04:35 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

C. Pagani (PSU), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), P. A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), O. Godet (U Leicester), D. Grupe (PSU),
C. Guidorzi (INAF-OAB), E. A. Hoversten (PSU), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), V. Mangano (INAF-IASFPA),
F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL),
T. Sakamoto (NASA/UMBC), B. Sbarufatti (INAF-IASFPA),
P. Schady (MSSL-UCL), M. C. Stroh (PSU), T. N. Ukwatta (GSFC/GWU),
P. A. Ward (MSSL-UCL) and H. Ziaeepour (UCL-MSSL) report on behalf of
the Swift Team:

At 12:50:05 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a possible burst (trigger=315630).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 35.570, +39.829 which is 
   RA(J2000) = 02h 22m 17s
   Dec(J2000) = +39d 49' 44"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a weak peak
with a duration of about 15 sec.  The peak count rate
was ~500 counts/sec (15-350 keV), at ~2 sec after the trigger. 
Given the weak significance of this detection, we can not say
if this is a real burst or not. 

The XRT began observing the field at 12:51:36.6 UT, 91.5 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 nominal 100 seconds with the White
(160-650 nm) filter starting 94 seconds after the BAT trigger. No afterglow
candidate has been found in the initial data products. Image catalog data are
not available at this time. 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 0.05. 




Burst Advocate for this burst is C. Pagani (pagani AT astro.psu.edu). 
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.)