Quasi-periodic oscillations in the long-term radio light curves of the blazar AO 0235+164

ABSTRACT We present time series analyses of three-decade long radio observations the BL Lacertae object AO 0235+164 made at University Michigan Radio Astronomical Observatory operating three central frequencies 4.8, 8.0, and 14.5 GHz. detected a quasi-periodic oscillation ∼965 d in all frequency bands light curve effectively simultaneous observations, along with strong signals ∼1950, ∼1350, ∼660 d. The periodicity is analysed methods: data-compensated discrete Fourier transform, generalized Lomb–Scargle periodogram, Weighted Wavelet Z-transform. These methods are chosen as they have different analysis approaches toward robust measurement claimed periodicities. 965 ± 50 found to be significant (at least 3.5σ) persistent throughout observation for frequencies, others, which may harmonics, comparably 8.0 GHz bands. briefly discuss plausible explanations origin such periodicity.