Letter to the Editor

Discovery of the preferred direction of electric vector position angle rotations in blazars

¹ Saint Petersburg State University, Universitetskaya nab. 7/9, St. Petersburg 199034, Russia
² Central (Pulkovo) Astronomical Observatory RAS, St. Petersburg 196140, Russia
³ Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215, USA
⁴ Institute of Astrophysics, Foundation research and Technology-Hellas, N. Plastira 100, Vassilika Vouton, GR-71110 Heraklion, Greece
⁵ Department of Physics, and Institute for Theoretical and Computational Physics, University of Crete, Voutes University campus, GR-70013 Heraklion, Greece
⁶ Crimean Astrophysical Observatory RAS, 298409 P/O Nauchny, Russia
⁷ Steward Observatory, The University of Arizona, Tucson, AZ 85721, USA

^⋆ Corresponding author; e.v.shishkina99@yandex.ru

Received: 12 August 2024
Accepted: 25 October 2024

Abstract

Blazars are a subclass of active galactic nuclei (AGNs) with a high optical linear polarization that originates in relativistic jets. Polarization parameters such as the degree of polarization (PD) and the electric vector position angle (EVPA) are directly related to the properties of the magnetic field in the jets. A study of the optical polarization of blazars allows conclusions to be drawn about the field geometry, its evolution, and its relation to the emission properties of the blazars. The periods of ordered changes in the electric vector position angle, so-called rotations, are of particular interest. We used a new method to determine EVPA rotations and to estimate their statistical significance with the aim to analyze long-term polarimetric observations of five blazars: OJ 287, S5 0716+71, 3C 454.3, CTA 102, and PG 1553+113. This resultes in the identification of 256 EVPA rotations. We found possible tendencies for the EVPA rotations to occur in a preferred direction in each of these sources: clockwise for OJ 287 and CTA 102, and counterclockwise for the others. The EVPA rotations can be explained by the spiral structure of the magnetic field in the jet. In this case, the observed preferred direction of rotations reflects the global structure of the magnetic field, which can be associated with the direction of rotation of either the black hole ergosphere or the accretion disk.