Optical monitoring of the Seyfert galaxy NGC 4151 from 1997 to 2003

CCD photometric observations (V, R, and I) of the Seyfert galaxy NGC 4151 were carried out from 1997 May 9 to 2003 May 25. A possible microvariation was found simultaneously in three bands on 2003 May 2. If the microvariation was due to a hot spot on the accretion disk, then there is probably a supermassive black hole of around 5.4 x 10(7) M-circle dot at the center of the source. Combining our new data and data from literature, the historical light curves from 1968 to 2003 (V band) and from 1910 to 2000 (B band) were compiled and used to study the periodicity of the source. A possible period of around 15.8 yr was found.