Fast radio bursts and their high-energy counterpart from magnetar magnetospheres

TL;DR

This paper proposes a model where fast radio bursts (FRBs) originate from crust fracturing in magnetars, producing coherent plasma radiation and associated X-ray bursts, with burst characteristics depending on magnetic field strength and crust activity.

Contribution

It introduces a novel mechanism linking magnetar crust fracturing to FRB generation and explains the correlated X-ray emissions and burst variability.

Findings

FRBs are triggered by crust fracturing near magnetic poles.

FRB-associated X-ray bursts result from magnetic field relaxation.

Stronger magnetic fields lead to brighter, more frequent bursts.

Abstract

The recent discovery of a Galactic fast radio burst (FRB) occurring simultaneously with an X-ray burst (XRB) from the Galactic magnetar SGR J1935+2154 implies that at least some FRBs arise from magnetar activities. We propose that FRBs are triggered by crust fracturing of magnetars, with the burst event rate depending on the magnetic field strength in the crust. Since the crust fracturing rate is relatively higher in polar regions, FRBs are preferred to be triggered near the directions of multipolar magnetic poles. Crust fracturing produces Alfv\'en waves, forming a charge starved region in the magnetosphere and leading to non-stationary pair plasma discharges. An FRB is produced by coherent plasma radiation due to nonuniform pair production across magnetic field lines. Meanwhile, the FRB-associated XRB is produced by the rapid relaxation of the external magnetic field lines. In this picture, the sharp-peak hard X-ray component in association with FRB 200428 is from a region between adjacent trapped fireballs, and its spectrum with a high cutoff energy is attributed to resonant Compton scattering. The persistent X-ray emission is from a hot spot heated by the magnetospheric activities, and its temperature evolution is dominated by magnetar surface cooling. Within this picture, magnetars with stronger fields tend to produce brighter and more frequent repeated bursts.