Detection of quasi-periodic oscillations in the long-term radio light curves of the blazar OT 081

Abstract

ABSTRACT We report the detection of quasi-periodic oscillations (QPOs) in the radio light curves at 4.8, 8, and 14.5 GHz of the blazar OT 081, by means of the Weighted Wavelet Z-transform (WWZ) and Lomb–Scargle periodogram (LSP) methods. The LSP diagrams and time-averaged WWZ powers demonstrate several significant claims of QPOs above the 4σ confidence level: QPOs of ∼850 and ∼1500 d in the 4.8-GHz light curve, ∼850, ∼1120, and ∼1540 d in the 8-GHz light curve, ∼850 and ∼1130 d in the 14.5-GHz light curve. The Keplerian orbit parameters in a binary black hole system have been estimated, assuming the QPO of ∼850 d appearing in all three wavebands is a real periodicity. Moreover, a pure geometrical scenario with blobs moving helically inside the jet provides another plausible explanation for the detected QPOs.