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 , { R _ { c } } , and { I _ { c } } 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 { \alpha } _ { 1 } = -0.59 ^ { +0.59 } _ { -0.44 } before and \alpha _ { 2 } = -1.43 \pm 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 \pm 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 { R _ { c } } =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 .