GCN Circular 6125

L. Vetere (PSU), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
S. Campana (INAF-OAB), M. M. Chester (PSU), N. Gehrels (NASA/GSFC),
D. Grupe (PSU), J. A. Kennea (PSU), W. B. Landsman (NASA/GSFC),
F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL),
M. Stamatikos (NASA/ORAU) and E. Troja (INAF-IASFPA) report on behalf
of the Swift Team:

At 01:15:00 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070223 (trigger=261664).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 153.452, +43.121 which is 
   RA(J2000)  =  10h 13m 49s
   Dec(J2000) = +43d 07' 16"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows several peaks
with a duration of about 50 sec.  The peak count rate
was ~1000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 01:16:50 UT, 110 seconds after the
BAT trigger. XRT found a bright, fading, uncatalogued X-ray source
located at RA, Dec 153.4533, +43.1336 which is
   RA(J2000)  =  10h 13m 48.7s
   Dec(J2000) =  43d 08' 00.9"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). 
This location is 45 arcseconds from the BAT on-board position,
within the BAT error circle. The initial flux in the 2.5s image
was 3.0e-09 erg/cm2/s (0.2-10 keV). 

UVOT took a finding chart exposure of nominal 100 seconds with the
White (160-650 nm) filter starting 120 seconds after the BAT trigger,
and a finding chart in V starting 226 seconds after the trigger. No
afterglow candidate has been found in the initial data products. 
Image catalog data are not available at this time. The 2.7'x2.7'
immediately available image covers 100% of the XRT 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
0.01.