A Neutron Star-White Dwarf Binary Model for Repeating Fast Radio Burst 121102

TL;DR

This paper proposes a binary system model involving a magnetic white dwarf and a neutron star to explain the repeating fast radio bursts observed in FRB 121102, emphasizing magnetic reconnection and Roche lobe overflow.

Contribution

It introduces a novel binary system model with magnetic reconnection and Roche lobe overflow to explain repeating FRBs, linking astrophysical processes to observed burst behavior.

Findings

The model can reproduce the frequency and timescale of FRB 121102.

Intermittent Roche lobe overflow explains the repeating nature of the bursts.

Magnetic reconnection accelerates electrons to produce curvature radiation.

Abstract

We propose a compact binary model for the fast radio burst (FRB) repeaters, where the system consists of a magnetic white dwarf (WD) and a neutron star (NS) with strong bipolar magnetic fields. When the WD fills its Roche lobe, mass transfer will occur from the WD to the NS through the inner Lagrange point. The accreted magnetized materials may trigger magnetic reconnection when they approach the NS surface, and therefore the electrons can be accelerated to an ultra-relativistic speed. In this scenario, the curvature radiation of the electrons moving along the NS magnetic field lines can account for the characteristic frequency and the timescale of an FRB. Owing to the conservation of angular momentum, the WD may be kicked away after a burst, and the next burst may appear when the system becomes semi-detached again through the gravitational radiation. By comparing our analyses with the observations, we show that such an intermittent Roche lobe overflow mechanism can be responsible for the observed repeating behavior of FRB 121102.