Optical EVPA rotations in blazars: testing a stochastic variability model with RoboPol data

TL;DR

This study examines optical polarization angle rotations in blazars using RoboPol data, testing a stochastic variability model which can replicate rotation parameters but not polarization fractions, suggesting some observed behaviors align with a random walk process.

Contribution

The paper tests a stochastic variability model against observed blazar polarization rotations, highlighting its strengths and limitations in explaining polarization behaviors.

Findings

Model reproduces rotation parameters similar to observations

Model fails to match polarization fraction data

Observations are consistent with a random walk process

Abstract

We identify rotations of the polarization angle in a sample of blazars observed for three seasons with the RoboPol instrument. A simplistic stochastic variability model is tested against this sample of rotation events. The model is capable of producing samples of rotations with parameters similar to the observed ones, but fails to reproduce the polarization fraction at the same time. Even though we can neither accept nor conclusively reject the model, we point out various aspects of the observations that are fully consistent with a random walk process.