Possible Quasi-Periodic modulation in the z = 1.1 $\gamma$-ray blazar PKS 0426-380

TL;DR

This study investigates potential quasi-periodic modulations in the gamma-ray and optical emissions of the distant blazar PKS 0426-380, finding significant gamma-ray periodicity but no confirmed optical periodicity, suggesting complex emission behaviors.

Contribution

First detection of gamma-ray quasi-periodicity in PKS 0426-380 using Fermi-LAT data with a period of about 3.35 years, highlighting the need for further multiwavelength observations.

Findings

Gamma-ray quasi-periodicity of 3.35 ± 0.68 years detected at ~3.6 sigma significance.

No significant optical-UV periodicity found, possibly due to incomplete data.

Further long-term monitoring required to confirm the periodicity.

Abstract

We search for $\gamma$-ray and optical periodic modulations in a distant flat spectrum radio quasar (FSRQ) PKS 0426-380 (the redshift $z=1.1$). Using two techniques (i.e., the maximum likelihood optimization and the exposure-weighted aperture photometry), we obtain $\gamma$-ray light curves from \emph{Fermi}-LAT Pass 8 data covering from 2008 August to 2016 December. We then analyze the light curves with the Lomb-Scargle Periodogram (LSP) and the Weighted Wavelet Z-transform (WWZ). A $\gamma$-ray quasi-periodicity with a period of 3.35 $\pm$ 0.68 years is found at the significance-level of $\simeq3.6\ \sigma$. The optical-UV flux covering from 2005 August to 2013 April provided by ASI SCIENCE DATA CENTER is also analyzed, but no significant quasi-periodicity is found. It should be pointed out that the result of the optical-UV data could be tentative because of the incomplete of the data. Further long-term multiwavelength monitoring of this FSRQ is needed to confirm its quasi-periodicity.