WWZ Analysis on the Variability Data of Quasar 3C 345

A new method to analyze unevenly-spaced data is described. It is based on the principle of wavelet analysis and called the weighted wavelet Z-transform (WWZ). Rather complete optical B-band data of the quasar 3C 345 in more than 100 years are collected to obtain its long-term light curve. With the WWZ method, the variability data from 1965 to 1992 are analyzed. The result shows that the data contain 3 periodical components, in which the periodicity of T = 4.54 ∼ 5.23 yr and T = 9.59 ∼ 11.51 yr is steady, while T = 624 ∼ 941 d is not a steady period.