TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  2024
SUBJECT: GRB 030329: Light curve observed during the change of its slope.
DATE:    03/03/30 15:17:40 GMT
FROM:    Rodion Burenin at IKI, Moscow  <rodion@hea.iki.rssi.ru>

R. Burenin, R. Sunyaev, M. Pavlinsky, D. Denissenko, O. Terekhov,
A. Tkachenko (IKI); Z. Aslan, K. Uluc, I. Khamitov (TUG); U. Kiziloglu,
A. Alpar, A. Baykal (METU); I. Bikmaev, N. Sakhibullin, V. Suleymanov (KSU)

report:

The optical afterglow of GRB 030329 (Peterson and Price, GCN 1985) was
observed with 1.5-m Russian-Turkish Telescope RTT150 at Bakyrlytepe (TUBITAK
National Observatory, Turkey). The observations started at Mar 29.744 UT,
appr. 6 hours after the burst and lasted until Mar 30.061 UT, appr. 14 hours
after the burst.

During the night we have obtained approximately 200 images in each BVRI
Bessel filter with 10-30 s exposures. The photometric conditions were good.

To calibrate the OT flux from the beginning of our observations we were
using the star which later was named as "A" star by Martini et al. (GCN
2012). We assume this star is R=16.20 which agree well with our mean
photometric solution, obtained in previous nights. To calibrate OT flux in
other filters we assume the following magnitudes of this star: B=18.22,
V=17.02, I=15.42, measured using the same photometric solutions.

The optical transient showed no significant variations above the gradual
decline; the preliminary upper limit on short-term variability is 5%.

In the first 5 hours of our run we find that the R-band flux declines as
t**-1.1. During the last 2.5 hours we observed the smooth continuous change
in the slope of power law flux decay.

The fit of the post-break light curve reported by Garnavich et al. (GCN
2018) lies exactly on the continuation of our light curve. This suggests
that we are lucky to observe in detail the major change in the slope of the
light curve and measure its duration. The break occured in 12-14 hours after
the burst and lasted for appr. 2-4 hours.

The R magnitudes of the afterglow are:
       
t-t0,hours   R
 6.199	    14.10
 7.049	    14.26
 7.899	    14.38
 8.749	    14.52
 9.599	    14.64
10.449	    14.75
11.299	    14.84
12.149	    14.96
12.999	    15.06
13.849	    15.16

The preliminary light curve in R can be found at
http://hea.iki.rssi.ru/~br/lcl_030329_r.ps

The finding chart available at http://hea.iki.rssi.ru/~br/r_030329.gif

Further analysys of the lightcurve is underway. 

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