The intraday variations of polarization vector direction in radio source S5 0716+714

TL;DR

This study presents high-resolution polarimetric monitoring of the blazar S5 0716+714, revealing rapid polarization variations linked to magnetic field precession, and introduces a numerical model to explain these phenomena.

Contribution

It introduces a numerical model of polarization in a jet with a precessing helical magnetic field to explain short-term polarization variations.

Findings

Polarization varies on 1-1.5 hour timescales.

Magnetic field precession with a period of about 15 days explains polarization changes.

Abstract

The bright radio source S5 0716+714, that is usually classified as BL Lac object, is one of the most intensively studied. S5 0716+714 demonstrates extremely peculiar properties such as the shortest time-scale of optical and polarimetric variations observed in blazars. In given paper, the results of 9-hour polarimetric monitoring of S5 0716+714 with the $\sim$70-second resolution, carried out by the 6-m telescope BTA of SAO RAS, are presented. The observation data analysis reveals the variability both in total and polarized light on the 1-1.5-hour time-scale. Since polarization is generated by plasma motion in the magnetic field, the variations of polarization vector are bounded with the magnetic field configuration and the average time-scales specify the size of the emitting region, unresolved directly. We suggest a processed numerically model of polarization in the jet with the precessing helical magnetic field. Fitting the model discovers that observed short-term variations with the complicated trajectory of polarization vector could be induced by the magnetic field precession with the period $T \approx 15$ days.