OPTICAL MONITORING OF 3C 390.3 FROM 1995 TO 2004 AND POSSIBLE PERIODICITIES IN THE HISTORICAL LIGHT CURVE

We report V, R, and I band CCD photometry of the radio galaxy 3C 390.3 obtained with the 1.56 m telescope of the Shanghai Astronomical Observatory from 1995 March to 2004 August. Combining these data with data from the literature, we have constructed a historical light curve from 1894 to 2004 and searched for periodicities using the CLEANest program. We find possible periods of 8.30 ± 1.17, 5.37 ± 0.49, 3.51 ± 0.21, and 2.13 ± 0.08 yr.