Multiwavelength Variability Analysis of the Blazar PKS 0727-11: A $\sim$168 Days Quasi-periodic Oscillation in Gamma-ray

TL;DR

This study detects a significant quasi-periodic oscillation of approximately 169 days in the gamma-ray light curve of the blazar PKS 0727-11, suggesting a possible supermassive binary black hole system as the underlying cause.

Contribution

First detection of periodic gamma-ray variability in PKS 0727-11, supported by multiple analysis methods and linked to a supermassive binary black hole model.

Findings

Detected a 168.6-day QPO in gamma-ray light curve

Strong correlation between gamma-ray and radio flares

Estimated black hole mass range of 3.66×10^8 to 5.79×10^9 solar masses

Abstract

We performed variability analysis of the multiwavelength light curves for the flat-spectrum radio quasar PKS 0727-11. Using the generalized Lomb-Scargle periodogram, we identified a possible quasi-periodic oscillation (QPO) of $\sim$ 168.6 days (persisted for 6 cycles, with a significance of $3.8\sigma$) in the gamma-ray light curve during the flare period (MJD 54687-55738). It is the first time that periodic variations have been detected in this source, and further supported by other methods: weighted wavelet $z$-transform, phase dispersion minimization, REDFIT, autoregressive integrated moving average model, and structure function analysis. Cross-correlation analysis shows that there is a strong correlation between multi-band light variations, indicating that gamma-ray and radio flares may originate from the same disturbance, and the distance between the emission regions of gamma-ray and radio flares is calculated based on the time lag. We demonstrate that QPO arising from the non-ballistic helical jet motion driven by the orbital motion in a supermassive binary black hole is a plausible physical explanation. In this scenario, the estimated mass of the primary black hole is $M\sim3.66\times10^8-5.79\times10^{9}M_\odot$.