Early (<0.3 Days) R -Band Light Curve of the Optical Afterglow of GRB 030329

We observed the optical afterglow of the bright gamma-ray burst GRB030329 onthe nights of 2003 March 29, using the Kiso observatory (the University ofTokyo) 1.05 m Schmidt telescope. Data were taken from March 29 13:21:26 UT to17:43:16 (0.072 to 0.253 days after the burst), using an $Rc$-band filter. Theobtained $Rc$-band light curve has been fitted successfully by a single powerlaw function with decay index of $0.891\pm0.004$. These results remainunchanged when incorporating two early photometric data points at 0.065 and0.073 days, reported by Price et al.(2003) using the SSO 40 inch telescope, andfurther including RTT150 data (Burenin et al. 2003) covering at about 0.3 days.Over the period of 0.065-0.285 days after the burst, any deviation from thepower-law decay is smaller than $\pm$0.007 mag. The temporal structure reportedby Uemura et al. (2003) does not show up in our $R$-band light curve.Comment: 9 pages, 2 figures, 1 table, accepted for publication in ApJ