Testing particle acceleration in blazar jets with continuous high-cadence optical polarization observations

TL;DR

This study presents the first continuous, high-cadence optical polarization observations of blazars over 24 hours, revealing rapid polarization variability and challenging existing particle acceleration models.

Contribution

It demonstrates the feasibility of global telescope networks for continuous blazar monitoring and compares observations with advanced plasma simulations, highlighting gaps in current models.

Findings

Detected sub-hour polarization variations in blazars.

Observed a rapid ~180° polarization angle rotation.

Simulations cannot fully explain observed polarization behavior.

Abstract

Variability can be the pathway to understanding the physical processes in astrophysical jets, however, the high-cadence observations required to test particle acceleration models are still missing. Here we report on the first attempt to produce continuous, >24 hour polarization light curves of blazars using telescopes distributed across the globe and the rotation of the Earth to avoid the rising Sun. Our campaign involved 16 telescopes in Asia, Europe, and North America. We observed BL Lacertae and CGRaBS J0211+1051 for a combined 685 telescope hours. We find large variations in the polarization degree and angle for both sources in sub-hour timescales as well as a ~180 degree rotation of the polarization angle in CGRaBS J0211+1051 in less than two days. We compared our high-cadence observations to Particle-In-Cell magnetic reconnection and turbulent plasma simulations. We find that although the state of the art simulation frameworks can produce a large fraction of the polarization properties, they do not account for the entirety of the observed polarization behavior in blazar jets.