[vsnet-grb-info 6468] GRB 080810: Swift detection of a burst with a bright optical afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8080
SUBJECT: GRB 080810: Swift detection of a burst with a bright optical afterglow
DATE:    08/08/10 13:31:39 GMT
FROM:    David Burrows at PSU/Swift  <dxb15 at psu.edu>

K. L. Page (U Leicester), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
P. A. Evans (U Leicester), C. Guidorzi (INAF-OAB),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
N. P. M. Kuin (MSSL), J. Mao (INAF-OAB), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL), M. Stamatikos (NASA/ORAU),
R. L. C. Starling (U Leicester) and T. N. Ukwatta (GSFC/GWU) report
on behalf of the Swift Team:

At 13:10:12 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080810 (trigger=319584).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 356.779, +0.320 which is 
   RA(J2000) = 23h 47m 07s
   Dec(J2000) = +00d 19' 11"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multiple-peaked
structure with a duration of about 140 sec, including a peak during the
time of the XRT/UVOT observations.  The peak count rate
was ~3000 counts/sec (15-350 keV), at ~22 sec after the trigger. 

The XRT began observing the field at 13:11:28.3 UT, 76.0 seconds after
the BAT trigger. XRT found a bright, flaring, uncatalogued X-ray source 
located at RA, Dec 356.7936, +0.3188 which is equivalent to:
  RA(J2000)  = 23h 47m 10.4s
  Dec(J2000) = +00d 19' 07.6"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 52 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

UVOT took a finding chart exposure of nominal 100 seconds with the White
(160-650 nm) filter starting 88 seconds after the BAT trigger. There is a
bright candidate afterglow in the list of sources generated on-board at
  RA(J2000)  =  23:47:10.5 = 356.79375
  DEC(J2000) = +00:19:10   =  +0.31944
with a 1-sigma error radius of about 1.0 arc sec. The estimated white
magnitude is 14.7 with a 1-sigma error of about 0.5 mag. No correction
has been made for a Galactic extinction corresponding to a reddening of
0.03 mag along the line of sight. 

We note the presence of the galaxy J234710.47+001906.0 
about 1.7 arcsec from the XRT position. 

Burst Advocate for this burst is K. L. Page (kpa 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.)