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

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.

Accepted for publication in Astronomy & Astrophysics. 10 pages, 5 figures. GitHub: https://github.com/glykanastasia/blazar-evpa-rotation-detector

References in corpus (19)

• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• The Spectral Energy Distribution of Fermi bright blazars
• Relativistic Jets in Active Galactic Nuclei
• Studies in Astronomical Time Series Analysis. VI. Bayesian Block Representations
• Turbulent, Extreme Multi-Zone Model for Simulating Flux and Polarization Variability in Blazars
• Blazar spectral variability as explained by a twisting inhomogeneous jet
• RoboPol: The optical polarization of gamma-ray--loud and gamma-ray--quiet blazars
• RoboPol: First season rotations of optical polarization plane in blazars
• RoboPol: optical polarization-plane rotations and flaring activity in blazars
• RoboPol: Connection between optical polarization plane rotations and gamma-ray flares in blazars
• The RoboPol optical polarization survey of gamma-ray - loud blazars
• The RoboPol Pipeline and Control System
• RoboPol: Do optical polarization rotations occur in all blazars?
• RoboPol: AGN polarimetric monitoring data
• Optical EVPA rotations in blazars: testing a stochastic variability model with RoboPol data
• Optical polarization map of the Polaris Flare with RoboPol
• The RoboPol Program: Optical Polarimetric Monitoring of Blazars
• Variability and evolution of the optical polarization of a sample of gamma-ray blazars
• The Method of Searching for Rotations of the Polarization Position Angle of Quasars