Revisiting radio variability of the blazar 3C 454.3

Abstract

We examine lengthy radio light curves of the flat spectrum radio galaxy 3C 454.3 for possible quasi-periodic oscillations (QPOs). The data used in this work were collected at five radio frequencies, 4.8, 8.0, 14.5, 22.0, and 37.0 GHz between 1979--2013 as observed at the University of Michigan Radio Astronomical Observatory, Crimean Astrophysical Observatory, and Aalto University Mets{\"a}hovi Radio Observatory. We employ generalized Lomb-Scargle periodogram and weighted wavelet transform analyses to search for periodicities in these light curves. We confirm a QPO period of $\sim$ 2000 day to be at least 4$\sigma$ significant using both methods at all five radio frequencies between 1979 and 2007, after which a strong flare changed the character of the light curve. We also find a $\sim$~600 day period which is at least 4$\sigma$ significant, but only in the 22.0 and 37.0 GHz light curves. We briefly discuss physical mechanisms capable of producing such variations.