Radiation-Driven Stellar Eruptions

TL;DR

This paper reviews the physics behind radiation-driven eruptions in very massive stars, discussing observational facts, proposed mechanisms, and the unresolved nature of giant eruptions and LBV events.

Contribution

It provides a comprehensive overview of the physics, observations, and theories related to radiation-driven stellar eruptions, highlighting unresolved questions and new conjectures.

Findings

Radiation pressure can drive colossal eruptions in massive stars.

Spectral and temperature characteristics depend on opaque outflow properties.

Multiple instability mechanisms are proposed but not definitively established.

Abstract

Very massive stars occasionally expel material in colossal eruptions, driven by continuum radiation pressure rather than blast waves. Some of them rival supernovae in total radiative output, and the mass loss is crucial for subsequent evolution. Some are supernova impostors, including SN precursor outbursts, while others are true SN events shrouded by material that was ejected earlier. Luminous Blue Variable stars (LBV's) are traditionally cited in relation with giant eruptions, though this connection is not well established. After four decades of research, the fundamental causes of giant eruptions and LBV events remain elusive. This review outlines the basic relevant physics, with a brief summary of essential observational facts. Reasons are described for the spectrum and emergent radiation temperature of an opaque outflow. Many proposed mechanisms are noted for instabilities in the star's photosphere, in its iron opacity peak zones, and in its central region. Some of the remarks and conjectures here have not yet become familiar in the published literature.