Intra-night optical polarization monitoring of blazars

TL;DR

This study presents the first intra-night optical polarization monitoring of blazars, revealing rapid variability and turbulence in magnetic fields that influence their emission models.

Contribution

It provides new observational data on intra-night polarization variability in blazars using RoboPol and other observatories, highlighting rapid changes on minute timescales.

Findings

Variability on timescales as short as minutes is common in blazar jets.

Polarization degree variations are typically a few percent.

Polarization angle remains relatively stable over time.

Abstract

Blazars are known for their extreme variability across the electromagnetic spectrum. Variability at very short timescales can push the boundaries between competing models offering us much needed discriminating power. This is particularly true for polarization variability that allows us to probe particle acceleration and high-energy emission models in blazars. Here we present results from the first pilot study of intra-night optical polarization monitoring conducted using RoboPol at the Skinakas Observatory and supplemented by observations from the Calar Alto, Perkins, and Sierra Nevada observatories. Our results show that while variability patterns can widely vary between sources, variability on timescales as short as minutes is prevalent in blazar jets. The amplitude of variations are typically small, a few percent for the polarization degree and less than 20 degrees for the polarization angle, pointing to a significant contribution to the optical emission from a turbulent magnetic field component, while the overall stability of the polarization angle over time points to a preferred magnetic field orientation.