TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1898
SUBJECT: GRB 030226, optical light curve
DATE:    03/02/27 15:41:57 GMT
FROM:    Sylvio Klose at TLS Tautenburg  <klose@tls-tautenburg.de>

A. Zeh, S. Klose (both TLS Tautenburg),
J. Greiner (MPE Garching),
J. Fynbo (University of Aarhus),
P. Jakobsson (University of Copenhagen),
on behalf of the GRACE collaboration

report:


Based on a compilation of all R-band data published so far on the
afterglow of GRB 030226 (von Braun et al., GCN 1881; Ando et al., GCN
1882; Garnavich, von Braun & Stanek, GCN 1885;  Price & Warren, GCN
1890; Guarnieri et al., GCN 1892; Greiner et al., GCN 1894) we have
fitted a preliminary light curve. Following Garnavich et al. (GCN
1885), we corrected the data published in GCNs 1881 and 1882 by 0.39
mag. For these data and for those reported in GCNs 1890 and 1892 we
estimated a conservative photometric error of 0.3 mag. Finally, we
included in the fit another data point based on observations with the
ESO NTT telescope last night.

Numerical fits were obtained with the formula of Beuermann et al. (1999;
A&A 352, L26). The result is:

       early-time slope:  alpha_1 = 0.62 +/- 0.19
       late-time  slope:  alpha_2 = 1.95 +/- 0.26
       break time:              t = 0.51 +/- 0.12 days,

assuming no contribution from an underlying host galaxy. So, we
confirm the earlier finding of Greiner et al. (GCN 1894) of a break in
the optical light curve less than 1 day after the burst. We note
that, if confirmed, these afterglow parameters are similar to those
found for GRB 010222 (e.g., Masetti et al. 2001, A&A 374, 382).

We publish the results of this fit in order to help observers to plan
their further observing strategy. The fitted light curve is posted at
http://www.mpe.mpg.de/~jcg/grb030226.html. Note that the data are not
corrected for Galactic extinction.