Rotation Measure Variations and Reversals of Repeating Fast Radio Bursts in Massive Binary Systems by Z. Y. Zhao et al. on Monday 28 November

Recent observations discovered that some repeating fast radio bursts (FRBs)

show complicated variations and reversals of Faraday rotation measures (RMs),

indicating that the sources of these FRBs are embedded in a dynamically

magnetized environment. One possible scenario is that repeating FRBs are

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 not reverse except if the magnetic axis

inclination angle is close to $90 ^\circ$. For the toroidal magnetic field in

the wind, RM will reverse at the super conjunction. For the case of the

toroidal field in the disc, the RM variations may have a multimodal and

multiple reversal profile because the radio signals travel through different

components of the disc during periastron passage. We also apply this model to

FRB 20180916B. By assuming its 16.35-day period is from a slowly rotating or

freely precessing magnetar, we find that the secular RM variation can be

explained by the periastron passage of a magnetar in a massive binary system.

In addition, 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 environments of repeating FRBs.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.05242v2