Random Polarization Position Angle Behaviors across Bursts of Repeating Fast Radio Bursts

TL;DR

This study analyzes the polarization position angle behaviors of repeating fast radio bursts, finding that their intrinsic angles follow a Gaussian distribution and show no periodicity, explained by a dynamic magnetosphere model.

Contribution

It introduces a model extending the rotating vector model to account for a dynamically evolving magnetosphere, explaining polarization behaviors without periodic signals.

Findings

Intrinsic PAs are approximately Gaussian distributed.

No credible periodicity detected in PA time series.

The model explains PA variations through a wandering magnetic axis.

Abstract

Fast radio bursts (FRBs), highly polarized, mostly have a nearly constant polarization position angle (PA) during each burst. Their PAs are observed to vary from burst to burst, with the statistical properties remaining stable across different observation sessions. We found that the intrinsic PAs of repeating FRBs are approximately Gaussian distributed, suggesting that the emission likely originates from a localized region within the neutron star's magnetosphere. A periodicity search of the PA time series using the Lomb-Scargle periodogram reveals no credible periodic signal in the period range from 10 ms to $10^7$ ms, and similar analyses of several active observations also yield null detections. We interpret these properties by extending the rotating vector model to include a dynamically evolving magnetosphere, in which the effective magnetic axis varies from burst to burst due to stochastic perturbations. In this framework, the observed PA distributions can naturally arise from geometric projection effects, and the absence of periodicity reflects the random wandering of the magnetic axis within a confined region. This scenario provides a natural explanation for both repeating and apparently non-repeating FRBs.