A Possible $\gamma$-ray Quasi-periodic Oscillation of $\sim$ 314 days in the Blazar OJ 287

TL;DR

This paper reports the detection of a probable 314-day gamma-ray quasi-periodic oscillation in the blazar OJ 287, using multiple analysis methods on Fermi-LAT data, suggesting possible links to radio jet features.

Contribution

It presents the first evidence of a gamma-ray QPO in OJ 287 around 314 days, analyzed with Lomb-Scargle, REDFIT, and wavelet methods, and discusses potential emission models.

Findings

Detection of a 314-day gamma-ray QPO in OJ 287

Use of multiple analysis techniques to confirm periodicity

Possible association with radio jet features

Abstract

We report the detection of a probable $\gamma$-ray quasi-periodic oscillation (QPO) of around 314 days in the monthly binned 0.1 -- 300 GeV $\gamma$-ray {\it Fermi}-LAT light curve of the well known BL Lac blazar OJ 287. To identify and quantify the QPO nature of the $\gamma$-ray light curve of OJ 287, we used the Lomb-Scargle periodogram (LSP), REDFIT, and weighted wavelet z-transform (WWZ) analyses. We briefly discuss possible emission models for radio-loud active galactic nuclei (AGN) that can explain a $\gamma$-ray QPO of such a period in a blazar. Reports of changes in the position of quasi-stationary radio knots over a yearly timescale as well as a strong correlation between gamma-ray and mm-radio emission in previous studies indicate that the signal is probably associated with these knots.