PREPRINT
1D18F8E4-3CE1-49B8-BDCB-08C2208DE60E

# Rotation Measure Variations and Reversals of Repeating Fast Radio Bursts in Massive Binary Systems

Z. Y. Zhao, G. Q. Zhang, F. Y. Wang, Z. G. Dai
arXiv:2209.05242

Submitted on 12 September 2022

## Abstract

Recent observations discovered that some repeating fast radio bursts (FRBs) show complex variations and reversals of Faraday rotation measures (RMs), indicating the sources of these FRBs are embedded in a dynamically magnetized environment. One possible scenario is that repeating FRBs generated by pulsars in binary systems, especially containing a high-mass companion with strong stellar outflows. Here, we study the RM variations caused by stellar winds, and a possible stellar disc. If the magnetic field is radial in the stellar wind, RM will reach the peak at periastron and will not reverse. For the toroidal magnetic field in the wind, RM will reverse at the super conjunction. The $|\mathrm{RM}|$ evolution is symmetric before and after the periastron for a radial magnetic field, or the super conjunction for a toroidal magnetic field. For the case of the toroidal field in the disc, the RM variations only occur at the time when the pulsar passes through the inclined disc before and after periastron. Our model can explain the secular RM variation of FRB 20180916B. Besides, the clumps in the stellar wind and disc can cause short time-scale ($<1$ day) variations or reversals of RM. Therefore, long-term monitoring of RM variations can reveal the origins of FRBs.

## Preprint

Comment: 16 pages, 4 figures, 2 tables, submitted

Subjects: Astrophysics - High Energy Astrophysical Phenomena; Astrophysics - Solar and Stellar Astrophysics