TITLE:   GCN CIRCULAR
NUMBER:  7936
SUBJECT: GRB 080703: Swift detection of a burst with optical afterglow
DATE:    08/07/03 19:17:07 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

H. Ziaeepour (UCL-MSSL), S. D. Barthelmy (GSFC), M. M. Chester (PSU),
J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), O. Godet (U Leicester),
H. A. Krimm (CRESST/GSFC/USRA), C. B. Markwardt (CRESST/GSFC/UMD),
F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester),
C. Pagani (PSU), K. L. Page (U Leicester), D. M. Palmer (LANL),
D. Perez (U Leicester), P. Schady (MSSL-UCL),
R. L. C. Starling (U Leicester), M. C. Stroh (PSU),
T. N. Ukwatta (GSFC/GWU), D. E. Vanden Berk (PSU) and
P. A. Ward (MSSL-UCL) report on behalf of the Swift Team:

At 19:00:13 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080703 (trigger=315819).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 101.867, -63.222 which is 
   RA(J2000)  =  06h 47m 28s
   Dec(J2000) = -63d 13' 19"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single peak
with a duration of about 5 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

Using promptly downlinked data we find a bright, uncatalogued
X-ray source. The position, astrometrically enhanced by aligning promptly
available UVOT field source  positions to the USNO-B1 catalogue, is RA,Dec =
101.80538,  -63.22039 (degrees) which is equivalent to:

RA  (J2000.0) =  06 47 13.29
DEC (J2000.0) =  -63 13 13.4

with an uncertainty of 3.04 arcsec (radius, 90% containment). 
This position is 100.1 arcsec from the BAT position, inside the BAT
error circle and 6.3 arcseconds from the UVOT position. 

UVOT took a finding chart exposure of nominal 100 seconds with the White
(160-650 nm) filter starting 100 seconds after the BAT trigger. There is a
candidate afterglow in the list of sources generated on-board at
  RA(J2000)  =  06:47:12.65 = 101.8027
  DEC(J2000) = -63:13:08.8  = -63.2191
with a 1-sigma error radius of about 0.8 arc sec. This position is 104.9 arc
sec. from the center of the BAT error circle. The estimated magnitude is 17.6
with a 1-sigma error of about 0.5 mag. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.07. 

Burst Advocate for this burst is H. Ziaeepour (hz AT mssl.ucl.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.)