Expanding fireball in magnetar bursts and fast radio bursts

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.

Automated summary

A radiation plasma fireball near the surface of a neutron star expands and produces photon emission and relativistic matter outflow along magnetic field lines. We classify the evolution of the expanding fireball into five cases, taking into account key processes such as lateral diffusion of photons, effects of strong magnetic field, baryon loading, and radiative acceleration. Applying this model to magnetar bursts with FRBs, we show that the burst radiation can accelerate the outflow to high-Lorentz factor with sufficient energy to power FRBs.