Quasiperiodic Polarized Emissions from Kink Structure in Magnetized Relativistic Jets

Abstract

Recent polarimetric observations of blazars indicate the development of current-driven (CD) kink instability after passing the recollimation shocks in the relativistic jets and association with quasiperiodic oscillations (QPOs). To investigate multiwavelength polarized features of CD kink instability in jets, we develop RaptorP, a new special relativistic module of the polarized general relativistic radiative transfer code RAPTOR. Based on 3D SRMHD simulations of overpressured magnetized jets, we find that jet images vary at different frequencies. At low frequencies, the emission comes from the turbulent ambient medium surrounding the jet that obscures the inner jet structure. Electric Vector Position Angle (EVPA) patterns are perpendicular to the jet propagation direction, indicating a dominance of the poloidal magnetic field. At high frequencies, bright knots and twisted kink structures appear, and EVPA patterns are consistent with a toroidal magnetic field. We also find QPOs in light curves of intensity and linear polarization (degree and angle). The peak frequency in power spectral densities is well matched with the rotation period of the kink structure in relativistic jets. It shows an anticorrelation between total intensity and the degree of polarization at a lower inclination angle. Our findings, based on realistic polarized radiation calculations, will explain the observational signatures seen in blazars. © 2025. The Author(s). Published by the American Astronomical Society.