Detection of an Optical Quasiperiodic Oscillation in the Blazar 3C 454.3

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Abstract
We analyzed 19 yr of R -band data of the blazar 3C 454.3 from the Whole Earth Blazar Telescope archive, along with new data from its members and from public archives such as those provided by the Small and Moderate Aperture Research Telescope System and the Steward Observatory projects to search for quasiperiodic oscillations (QPOs). We detected a QPO of ∼433 days using Lomb–Scargle periodogram, which lasted from MJD 54980–58450 as detected by the weighted wavelet Z-transform technique, making it one of the most persistent QPOs ever detected in the optical regime. The phase dispersion minimization technique was also performed to further validate this QPO claim. We detected this signal at a global significance of 2.53 σ across all methodologies. To explain the observed QPO, we have considered both models focused on the accretion disk around a supermassive black hole (SMBH), and those based purely on jet emissions. Plausible jet-based models involve a shock moving down the jet in a helical magnetic field, whereas the SMBH models could involve Lense–Thirring-effect-induced jet precession or dual jets in a binary SMBH system. We introduce a novel approach to distinguish genuine QPOs from spurious signals arising from annual seasonal gaps, a common limitation of ground-based observations.

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