Quasi-periodic oscillation detected in $\gamma$-rays in blazar PKS 0346-27

TL;DR

This study detects a ~100-day quasi-periodic oscillation in the gamma-ray emission of blazar PKS 0346-27, suggesting jet curvature and helical motion as the likely cause, with high statistical significance.

Contribution

First detection of a significant gamma-ray quasi-periodic oscillation in PKS 0346-27, linking it to jet curvature and helical motion, using robust statistical and modeling methods.

Findings

Detected a ~100-day QPO with 3σ significance.

Global significance of the QPO is 96.96%.

Modeling indicates jet curvature and helical motion as the likely origin.

Abstract

We present a variability study of the blazar PKS 0346-27 from December 2018 to January 2022 in its archival $\gamma$-ray observation by Fermi-LAT. We use the Lomb-Scargle periodogram and the weighted wavelet transform methods in order to detect the presence of periodicity/quasi-periodicity and localize this feature in time and frequency space. The significance of the periodicity feature has been estimated using the Monte-Carlo simulation approach. We have also determined the global significance of the periodicity to test the robustness of our claim. To explore the most probable scenario, we modeled the light curve with both a straight jet and a curved jet model. We detect a periodicity feature of $\sim$ 100 days duration for the entire period of observation with a statistical significance of $3\sigma$, which amounts to a 99.7\% confidence level. The global significance of this feature is found to be 96.96\%. Based on the Akaike Information Criteria, the most probable explanation is that the observed emission is enhanced due to the helical motion of a blob within a curved jet. The origin of this QPO is very likely a region of enhanced emission moving helically inside a curved jet. This work presents strong evidence for jet curvature in the source and an independent (albeit a little serendipitous) procedure to estimate the curvature in blazar jets.