Eruption of the Envelope of Massive Stars by Energy Injection with Finite Duration

TL;DR

This study uses radiation hydrodynamical simulations to investigate how energy injection at the base of a red supergiant's envelope can cause eruptive mass loss, highlighting the importance of energy injection rate and timescale.

Contribution

It provides the first detailed analysis of the effects of finite-duration energy injection on eruptive mass loss in massive stars, linking injection parameters to CSM formation.

Findings

Eruption requires energy injection rate above a critical threshold.

Density profile of CSM is consistent with analytical predictions for finite injection times.

Eruption depends on energy injection exceeding the envelope's binding energy over the dynamical timescale.

Abstract

A significant fraction of supernovae show signatures of dense circumstellar material (CSM). While multiple scenarios for creating a dense CSM exist, mass eruption due to injection of energy at the base of the outer envelope is a likely possibility. We carry out radiation hydrodynamical simulations of eruptive mass loss from a typical red supergiant progenitor with initial mass of $15\ M_\odot$, for the first time focusing on the timescale of the injection as well as energy. We find that not only sufficient injection energy but also sufficient rate of energy injection per unit time, $L_{\rm{min}} \sim 8\times 10^{40}$ erg s$^{-1}$ in this particular model, is required for eruption of unbound CSM. This result suggests that the energy injection rate needs to be greater than the binding energy of the envelope divided by the dynamical timescale for the eruption. The density profile of the resulting CSM, whose shape was analytically and numerically predicted in the limit of instantaneous energy injection, similarly holds for a finite injection timescale. We discuss our findings in the framework of proposed mass outburst scenarios, specifically wave-driven outbursts and common envelope ejection.