Repeating fast radio burst 20201124A originates from a magnetar/Be star binary

TL;DR

This paper proposes that the repeating FRB 20201124A originates from a binary system with a magnetar and a Be star, explaining observed magnetic and propagation variations through the interaction with the Be star's disk.

Contribution

It introduces a physical model linking FRB 20201124A's properties to a magnetar/Be star binary system, explaining observed magnetic and propagation phenomena.

Findings

Variation in Faraday rotation measure explained by magnetic field reversal.

Radio wave propagation affected by Be star's decretion disk during periastron.

Model predicts FRBs can originate from Be/X-ray binary systems.

Abstract

Fast radio bursts (FRBs) are cosmic sources emitting millisecond-duration radio bursts. Although several hundreds FRBs have been discovered, their physical nature and central engine remain unclear. The variations of Faraday rotation measure and dispersion measure, due to local environment, are crucial clues to understanding their physical nature. The recent observations on the rotation measure of FRB 20201124A show a significant variation on a day time scale. Intriguingly, the oscillation of rotation measure supports that the local contribution can change sign, which indicates the magnetic field reversal along the line of sight. Here we present a physical model that explains observed characteristics of FRB 20201124A and proposes that repeating signal comes from a binary system containing a magnetar and a Be star with a decretion disk. When the magnetar approaches the periastron, the propagation of radio waves through the disk of the Be star naturally leads to the observed varying rotation measure, depolarization, large scattering timescale, and Faraday conversion. This study will prompt to search for FRB signals from Be/X-ray binaries.