Quasi-periodic behaviour in the radio and γ-ray light curves of blazar PKS 1510–089

Abstract

Abstract We explore the possible quasi-periodic oscillations (QPOs) of the blazar PKS 1510–089, utilizing the ∼38-year Metsähovi flux density observations at 37 GHz and over ten-year Fermi-LAT observations in the 0.1–300 GeV energy range. Both the flux distributions of the radio and γ-ray light curves suggest a log-normal distribution, and power spectral densities (PSDs) of both light curves can be well represented by a bending power-law model. Comparing the results from the Weighted Wavelet Z-transform and Lomb-Scargle Periodogram approaches, a quasi period of 1330 ± 55 days at a 99.80% (>3σ) significance against the red noise background is observed in the radio light curve, whereas no similar modulation is seen in the γ-ray light curve. We briefly discuss the research actuality of blazar QPO phenomena and explain the observed radio QPO as the result of Keplerian motion in a supermassive binary black hole system and periodic modulation induced by the Lense-Thirring precession of the innermost portions of the accretion disk.