Fast radio bursts generated by coherent curvature radiation from compressed bunches for FRB 20190520B

TL;DR

This paper proposes a model where compressed charged bunches in a magnetized neutron star's magnetosphere produce coherent curvature radiation, explaining various observed features of FRB 20190520B.

Contribution

It introduces a novel mechanism involving ICS-induced compression of particle bunches to generate coherent curvature radiation in FRBs.

Findings

The model explains frequency downward drifting in FRB 20190520B.

It accounts for bright spots within dynamic spectra.

The formation of bunches is feasible within the proposed parameter space.

Abstract

The radiation mechanism of fast radio bursts (FRBs) has been extensively studied but still remains elusive. Coherent radiation is identified as a crucial component in the FRB mechanism, with charged bunches also playing a significant role under specific circumstances. In the present research, we propose a phenomenological model that draws upon the coherent curvature radiation framework and the magnetized neutron star, taking into account the kinetic energy losses of outflow particles due to inverse Compton scattering (ICS) induced by soft photons within the magnetosphere. By integrating the ICS deceleration mechanism for particles, we hypothesize a potential compression effect on the particle number density within a magnetic tube/family, which could facilitate achieving the necessary size for coherent radiation in the radial direction. This mechanism might potentially enable the dynamic formation of bunches capable of emitting coherent curvature radiation along the curved magnetic field. Moreover, we examine the formation of bunches from an energy perspective. Our discussion suggests that within the given parameter space the formation of bunches is feasible. Finally, we apply this model to FRB 20190520B, one of the most active repeating FRBs discovered and monitored by FAST. Several observed phenomena are explained, including basic characteristics, frequency downward drifting, and bright spots within certain dynamic spectral ranges.