[vsnet-grb-info 7076] GRB 081211: Swift/UVOT detection of an optical afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8656
SUBJECT: GRB 081211: Swift/UVOT detection of an optical afterglow
DATE:    08/12/11 21:33:35 GMT
FROM:    Stefan Immler at NASA/GSFC  <stefan.m.immler at nasa.gov>

S. Immler (CRESST/UMD/GSFC), S. T. Holland (CRESST/USRA/GSFC), and H. A. 
Krimm (CRESST/GSFC/USRA) report on behalf of the Swift UVOT team:

Further analysis of Swift Ultraviolet/Optical Telescope (UVOT) data of 
GRB 081211 (Krimm et al., GCN Circ. 8653), starting 113 sec after the 
BAT trigger, gives a detection of an optical source within the enhanced 
Swift-XRT position (Beardmore et al., GCN Circ. 8655) at
     RA (J2000)  21:52:27.97 = 328.11654 (deg)
     Dec (J2000) -33:50:08.3 = -33.83565 (deg)
with an uncertainty of 0.7 arcseconds (radius, 90% containment) in the 
white filters at 4.5-sigma level of confidence. The source is not 
present in DSS, the USNO-B1.0 catalogue, or the 2MASS point source 
catalogue. It is not detected in any of the other UVOT filters at the 
limiting magnitudes reported below.

Filter Tstart(s) Tstop(s)  Exp(s)  Magnitude

wh     113       7134     588      21.23+/-0.39
u      326       6724     265      >20.23  (3-sigma UL)
b      582        741     293      >20.24  (3-sigma UL)
uvw2   632       7318     371      >20.40  (3-sigma UL)
v      656      11966     386      >19.38  (3-sigma UL)
uvm2   681       6314     136      >19.58  (3-sigma UL)
uvw1   706       6519     196      >19.87  (3-sigma UL)

The values quoted above are in the UVOT photometric system (Poole et al. 
2008, MNRAS, 383, 627) and are not corrected for the expected Galactic 
extinction along the line of sight which corresponds to a reddening of 
E(B-V)=0.077 mag (Schlegel et al. 1998).