Automating the detection of polarization angle rotations in blazars. Re-analysis of RoboPol data reveals 27 new rotations

TL;DR

This paper introduces an automated pipeline for detecting polarization angle rotations in blazars, revealing 27 new rotations and enabling more objective, reproducible analysis of jet dynamics.

Contribution

The authors developed a novel automated method combining Bayesian Blocks and statistical validation, improving detection accuracy and revealing previously unreported EVPA rotations.

Findings

Identified 27 new EVPA rotations in RoboPol data.

Rotations have amplitudes from 90.8° to 359.7° and durations of 7 to 111 days.

Longer rotations are associated with increased gamma-ray activity.

Abstract

We present an automated pipeline for the detection of EVPA rotations in blazars, integrating correction of the 180$^\circ$ ambiguity, Bayesian Blocks segmentation, and statistical validation. Applied to RoboPol monitoring data, the method identified 48 rotations across 25 sources, including multiple events in RBPLJ2232+1143, RBPLJ1751+0939, RBPLJ1800+7828, and RBPLJ2253+1608. The rotations span amplitudes from 90.8$^\circ$ to 359.7$^\circ$, durations between 7.0 and 111.3 days, and rotation rates averaging 5.0$^\circ$/day. Comparison with previous catalogs reveals systematic differences: Bayesian Blocks rotations are on average $\sim$10\% larger in amplitude, about twice as long in duration, and roughly two-thirds slower in angular velocity, reflecting systematic biases between adaptive binning and manual segmentation. In addition, we report 27 previously unreported rotations, including 11 from the final 2016--2017 season. A correlation analysis with contemporaneous Fermi--LAT $\gamma$-ray light curves shows that longer rotations tend to coincide with enhanced $\gamma$-ray activity, while rotation amplitude alone is not predictive of $\gamma$-ray brightness. Our pipeline minimizes subjective biases, expands the list of known EVPA rotations, and provides a reproducible framework for future multiwavelength studies of blazar jet dynamics and particle acceleration.