Periodicity analysis of the radio light curve of the Seyfert galaxy III Zw 2

We have analyzed the radio light curves of the Seyfert galaxy III Zw 2 at 22 and 37 GHz taken from the database of Metsähovi Radio Observatory, and found evidence of quasi-periodic activity. The light curves show great activity, with very complicated non-sinusoidal variations. Period of Pobs=5.14±0.19yr was consistently identified by three methods: the Jurkevich method, the power spectrum intensity estimation method and the discrete correlation function method. The variability period of about 5.14 yr in III Zw 2 is caused most likely by the helical motion of the jet.