TITLE:   GCN CIRCULAR
NUMBER:  7794
SUBJECT: GRB 080603B: Swift detection of a burst with optical afterglow
DATE:    08/06/03 19:59:18 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

V. Mangano (INAF-IASFPA), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), P. J. Brown (PSU),
G. Cusumano (INAF-IASFPA), N. Gehrels (NASA/GSFC),
C. Guidorzi (INAF-OAB), S. T. Holland (CRESST/USRA/GSFC),
J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA),
N. P. M. Kuin (MSSL), C. B. Markwardt (CRESST/GSFC/UMD),
F. E. Marshall (NASA/GSFC), K. M. McLean (GSFC/UMD),
P. T. O'Brien (U Leicester), C. Pagani (PSU), D. M. Palmer (LANL),
A. M. Parsons (GSFC), J. L. Racusin (PSU), T. Sakamoto (NASA/UMBC),
B. Sbarufatti (INAF-IASFPA), M. Stamatikos (NASA/ORAU),
T. N. Ukwatta (GSFC/GWU), D. E. Vanden Berk (PSU) and
H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team:

At 19:38:13 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080603B (trigger=313087).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 176.528, +68.076 which is 
   RA(J2000)  =  11h 46m 07s
   Dec(J2000) = +68d 04' 33"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows three main peaks
with a duration of about 70 sec.  The peak count rate
was ~8000 counts/sec (15-350 keV), at ~2 sec after the trigger. 

The XRT began observing the field at 19:39:55 UT. XRT found a bright, 
uncatalogued X-ray source located at:
   RA(J2000)  = 11h 46m 07.7s
   Dec(J2000) = +68d 03' 35.2"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). 

UVOT took a finding chart exposure of nominal 100 seconds with the White
(160-650 nm) filter starting 72 seconds after the BAT trigger. There is a
candidate afterglow in the list of sources generated on-board at
  RA(J2000)  =	11:46:07.70 = 176.5321
  DEC(J2000) = +68:03:40.0  =  68.0611
with a 1-sigma error radius of about 0.5 arc sec. This position is 4.9 arc sec. 
from the center of the XRT error circle. The estimated magnitude is 15.9 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 0.01. 

Burst Advocate for this burst is V. Mangano (vanessa AT ifc.inaf.it). 
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.)