GCN Circular 1923

S. Klose, B. Stecklum, A. Zeh (all TLS Tautenburg),
J. Greiner (MPE Garching),
A. A. Henden (USRA/USNO, Flagstaff),
on behalf of the GRACE collaboration

report:

We have continued our efforts of a multi-color imaging of the optical/
near-infrared afterglow of GRB 030226 with the ESO VLT telescopes at
Paranal.

Observations performed 4 days after the burst clearly show a source
at the position of the optical transient (OT; Price et al., GCN
1880
Not found
 
 
). This source is detected in all photometric bands. Based on an
aperture photometry, a comparison of the pre-break
optical/near-infrared colors of the optical transient with its
post-break colors reveals no apparent differences. Although this
result is still preliminary and small differences might still
be detectable based on a more accurate PSF photometry, we conclude:
To a good approximation, the break in the light curve was
achromatic and at the time of the VLT observations the OT's light
was still dominated by the afterglow.

A first inspection of the data obtained 4 days after the burst seemed
to confirm a further steepening of the light curve in all bands some
days after the burst (Kulkarni et al., GCN 1911
Not found
 
 
). However, our data do
not rule out the possibility that the reported steepening was a
temporary fluctuation between t ~2 and 3...4 days after the burst. In
particular, very recent VLT/FORS data show that the overall brightness
evolution of the OT still follows the predicted light curve (Zeh et
al., GCN 1898
Not found
 
 
) with alpha_2 ~2 (assuming that we do not begin to see
the host galaxy).

We are grateful for the assistence of the staff at Paranal.