V. Simon, R. Hudec (Astronomical Institute AV CR, Ondrejov) and
G. Pizzichini, N. Masetti (ITESRE, Bologna) report:
We have determined the color indices of the optical afterglow of
GRB011211 from the available data (GCN 1199, GCN 1200, GCN 1209),
using the calibration by Henden et al. (GCN 1197). The interpolation
method described in Simon et al. (2001, A&A, 377, 450) was used. The
indices of the afterglow of GRB011211 are:
t-To=0.503 days: V-R=0.39; R-I=0.42
t-To=1.183 days: B-V=0.52; V-R=0.44; R-I=0.53
t-To=1.463 days: V-R=0.28; R-I=0.60
The typical error of these indices is about 0.10 - 0.15 mag.
The Galactic reddening E(B-V)=0.042, determined from the maps by
Schlegel et al. (1998, ApJ, 500, 525), is comparable to the
errors of the measurements and can be neglected here.
These indices are close to the mean values of a sample of 17
afterglows (Simon et al. 2001) which yield (B-V)o=0.47+/-0.17,
(V-R)o=0.40+/-0.13, (R-I)o=0.46+/-0.18. This suggests that the
shape of the spectrum of the afterglow of GRB011211 is very similar
to the other afterglows and that its intrinsic reddening (that is
inside the host galaxy) must be again quite small (Simon et al.
2001). The search for the host galaxy and the determination
of its type are therefore encouraged.