Polarization swings in blazars

Abstract

We present a model of blazar variability that can both reproduce smooth large polarization angle swings, and at the same time allow for the seemingly random behaviour of synchrotron fluxes, polarization fraction and, occasionally, $\pi$/2 polarization jumps. We associate blazar flaring activity with a jet carrying helical magnetic fields and propagating along a variable direction (and possibly with a changing bulk Lorentz factor). The model predicts that for various jet trajectories (i) EVPA can experience large smooth temporal variations while at the same time polarization fraction ($\Pi$) can be highly variable; (ii) $\Pi \sim 0$ near sudden EVPA jumps of 90${}^{\circ }$, but can also remain constant for large, smoother EVPA swings; (iii) the total angle of EVPA rotation can be arbitrary large; (iv) intensity I is usually maximal at points of fastest EVPA changes, but can have a minimum. Thus, even for a regular, deterministic motion of a steadily emitting jet the observed properties can vary in a non-monotonic and/or seemingly stochastic way. Intrinsic fluctuations of the emissivity will further complicated the intensity profiles, but are expected to preserve the polarization structure.

11 pages, 18 figures, 2 tables; accepted for publication by MNRAS

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Cited by in corpus (10)

• RoboPol: Connection between optical polarization plane rotations and gamma-ray flares in blazars
• Relativistic rotating vector model for X-ray millisecond pulsars
• A peculiar multi-wavelength flare in the Blazar 3C 454.3
• The Polarization Behavior of Relativistic Synchrotron Self-Compton Jets
• Testing two-component models on very-high-energy gamma-ray emitting BL Lac objects
• H.E.S.S. detection of very-high-energy gamma-ray emission from the quasar PKS 0736+017
• A Model of Polarisation Rotations in Blazars from Kink Instabilities in Relativistic Jets
• Optical polarization variations in the blazar PKS 1749+096
• The RoboPol Program: Optical Polarimetric Monitoring of Blazars
• Progress in Multiwavelength and Multi-Messenger Observations of Blazars and Theoretical Challenges