Quasi-periodic behaviour in the $\gamma$-ray light curve of the blazar PKS 0405-385

TL;DR

This study detects a quasi-periodic oscillation of approximately 2.8 years in the gamma-ray light curve of blazar PKS 0405-385, supported by multiple analysis methods, suggesting possible jet dynamics or black hole binary origins.

Contribution

The paper presents a multi-method analysis confirming a 2.8-year QPO in PKS 0405-385's gamma-ray emission, linking optical and gamma-ray periodicities, and discussing potential physical mechanisms.

Findings

QPO detected with ~4.3σ significance in gamma-ray data

Optical and gamma-ray periodicities are consistent

Possible explanations include jet helical motion or black hole binary

Abstract

We analyze the quasi-periodic oscillation (QPO) of the historical light curve of FSRQs PKS 0405-385 detected by the Fermi LAT from August 2008 to November 2021. To identify and determine the QPO signal of PKS 0405-385 in the $\gamma$-ray light curve, we use four time series analysis techniques based on frequency and time domains, i.e., the Lomb-Scargle periodogram (LSP), the weighted wavelet z-transform (WWZ), the REDFIT and the epoch folding. The results show that PKS 0405-385 has a quasi-periodic behavior of $\sim$2.8 yr with the significance of $\sim$4.3$\sigma$ in Fermi long-term monitoring. Remarkably, we also performed QPO analysis in the G-band light curve observed from October 2014 to October 2021 using LSP and WWZ technology, and the results ($\sim$4$\sigma$ of significance) are consistent with the periodic detection in $\gamma$-ray. This may imply that the optical emission is radiated by an electron population same as the \gr\ emission. In discussing the possible mechanism of quasi-periodic behavior, either the helical motion within a jet or the supermassive black hole binary system provides a viable explanation for the QPO of 2.8 yr, and the relevant parameters have been estimated.