NUMBER:  2321
SUBJECT: GRB0 30725 : optical observations
DATE:    

B. L. Jensen (U. Copenhagen), J. Gorosabel (IAA-CSIC/STScI), J. Hjorth, C. Vinter (U. Copenhagen), J. U. Fynbo (ESO), P. M. Vreeswijk (ESO Chile) report:

We have, further to Vinter et al. (GCN #2335), continued to monitor the afterglow candidate (Monard, GCN 2324, GCN 2334) of GRB 030725 with the Danish 1.5m telescope at La Silla. The R-band observations of the transient source (at (RA,Dec)(J2000.0) = (20:33:59.47,-50:40:56.4)) has been obtained for 7 epochs during the period Jul. 29 to Aug. 05, 2003 UT.

The photometric calibration has been based on fixing USNO-star UO375_38889915 ((RA,Dec)(J2000.0) = (20:33:51.93,-50:41:17.6)) at R=17.0. The R-band data provides a reasonable fit to a powerlaw decay with slope \alpha = -1.4+-0.1. As this behaviour is typical of GRB optical afterglows, the afterglow interpretation of this source is strongly supported. Lightcurves are available at: http://www.astro.ku.dk/~brian_j/grb/grb030725/ "