  We present a photometric study of the optical counterpart of the
long-duration Gamma Ray Burst (GRB) 030725, which triggered the HETE FREGATE
and WXM instruments on July 25th, 2003, and lasted more than 160s. An optical
counterpart was identified at the Bronberg Observatory in South Africa about 7
hours after the burst occurred. The optical afterglow (OA) was observed between
4 and 15 days after the burst with the 1.54m Danish telescope at La Silla in
the V, Rc, and Ic bands. We fit a broken power law to the data and determine a
break time in the light curve between 16 hours and 4.7 days after the first
detection of the burst. The decay slope is alpha1 = -0.59 +0.59/-0.44 before
and alpha2 = -1.43 +/- 0.06 after the break. A bump may be present in the light
curve, only significant at the 2-sigma level, 13.9 days after the main burst.
The spectral slope of the OA, measured 12 days after the burst, is -2.9 +/- 0.6
, i.e. it falls in the extreme red end of the distribution of previous OA
spectral slopes. Observations of the field 8 months after the burst with the
EMMI instrument on the NTT telescope (La Silla) resulted in an upper limit of
Rc=24.7 mag for the host galaxy of GRB 030725. The OA of GRB 030725 was
discovered at a private, non-professional observatory and we point out that
with the current suite of gamma ray satellites, an effort to organize future
contributions of amateur observers may provide substantial help in GRB light
curve follow up efforts.
