Radiatively driven evaporation from magnetar's surface

TL;DR

This paper investigates how intense, E-mode dominated radiation from magnetar flares causes surface matter ablation, forming baryonic winds and a sheath around the fireball, explaining observed super-Eddington luminosities.

Contribution

It introduces a model of surface ablation and wind formation driven by radiative cross-section suppression in magnetar flares, highlighting the role of E- and O-mode photon interactions.

Findings

E-mode photons are scattered and partly converted to O-photons.

O-mode radiation exerts high pressure, expelling plasma.

A baryonic wind forms around the fireball, especially near polar caps.

Abstract

The luminosity of the Soft Gamma Repeater (SGR) flares significantly exceeds the Eddington luminosity. This is because they emit mainly in the E-mode, for which the radiative cross-sections are strongly suppressed. The energy is released in the magnetosphere forming a magnetically trapped pair fireball, and the surface of the star is illuminated by the powerful radiation from the fireball. We study the ablation of the matter from the surface by this radiation. The E-mode photons are scattered within the surface layer, partly being converted into O-photons, whose scattering cross-section is of the order of the Thomson cross-section. The high radiation pressure of the O-mode radiation expels the plasma upwards. The uplifted matter forms a thick baryon sheath around the fireball. If an illuminated fraction of the star's surface includes the polar cap, a heavy, mildly relativistic baryonic wind is formed.