Evidence for quasi-periodic oscillations in the optical polarization of the blazar PKS 2155-304

TL;DR

This paper reports the first detection of quasi-periodic oscillations in the optical polarization of the blazar PKS 2155-304, with periods around 13 and 30 minutes, during a high gamma-ray state, suggesting new ways to study active galactic nuclei.

Contribution

It provides the first evidence of QPOs in the polarization of an active galactic nucleus, revealing new observational phenomena in blazar studies.

Findings

Detection of a 13-minute QPO with >99.7% significance

Detection of a 30-minute QPO with >99% significance

QPOs observed during a period of enhanced gamma-ray brightness

Abstract

Evidence for the presence of quasi-periodic oscillations (QPOs) in the optical polarization of the blazar PKS 2155-304, during a period of enhanced gamma-ray brightness, is presented. The periodogram of the polarized flux revealed the existence of a prominent peak at $T\sim 13$ min, detected at >99.7% significance, and $T\sim 30$ min, which was nominally significant at >99%. This is the first evidence of QPOs in the polarization of an active galactic nucleus, potentially opening up a new avenue of studying this phenomenon.