The Detection of Possible γ-Ray Quasi-periodic Modulation with ∼600 days from the Blazar S2 0109+22

Abstract

In this work, we analyzed the long-term γ-ray data by a Fermi Large Area Telescope of blazar S2 0109+22, ranging from 2008 to 2023. The quasi-periodic oscillations (QPOs) of blazars aided in investigating the physical properties of internal supermassive black holes, the nature of variability, and the underlying radiation mechanism. We employed four different methods—Weighted Wavelet Z-transform, Lomb–Scargle periodogram, REDFIT and phase folded light curve analysis, for searching QPO signals. Our analysis identified a possible QPO behavior with a periodicity of ∼600 days in 2013 November–2023 January at a significance level of ∼3.5σ. This QPO signal sustained ∼9 yr, corresponding to 5.6 cycles, which was in good agreement with the previously observed periodicity of ∼657 days in radio. We explained this phenomenon based on the accretion model and the lighthouse effect, in a binary black hole system.