Expanding Fireball in Magnetar Bursts and Fast Radio Bursts

TL;DR

This paper models the expansion of radiation plasma fireballs near neutron stars, incorporating magnetic and baryonic effects, to explain how magnetar bursts can produce relativistic outflows capable of powering fast radio bursts.

Contribution

It introduces a comprehensive classification of fireball evolution near neutron stars, including effects like magnetic fields and baryon loading, and applies this to magnetar bursts linked to FRBs.

Findings

Fireball models can produce high Lorentz factor outflows.

Magnetar bursts can generate sufficient energy for FRBs.

Inclusion of magnetic and baryonic effects enhances understanding of burst dynamics.

Abstract

A fireball of radiation plasma created near the surface of a neutron star (NS) expands under its own pressure along magnetic field lines, and produces photon emission and relativistic matter outflow. We comprehensively classify the expanding fireball evolution into five cases and obtain the photospheric luminosity and the kinetic energy of the outflow, taking into account key processes; lateral diffusion of photons escaping from a magnetic flux tube, effects of strong magnetic field, baryon loading from the NS surface, and radiative acceleration via cyclotron resonant scattering, some of which have not been considered in the context of gamma-ray bursts. Applying our model to magnetar bursts with fast radio bursts (FRBs), in particular the X-ray short bursts from SGR 1935+2154 associated with the Galactic FRB 20200428A, we show that the burst radiation can accelerate the outflow to high Lorentz factor with sufficient energy to power FRBs.