Envelope Inflation and outflow Driven by Energy Deposition in Massive Stars

Abstract

Evolved massive stars are known to undergo outflow with high mass ejections, resulting in the loss of a substantial portion of their envelopes. One proposed mechanism driving these events is the release or deposition of energy within the stellar envelope. We use a one-dimensional hydrodynamical code to investigate the resulting outflow and stellar response to energy deposition at specific regions inside a $\rm 70 \, M_{\odot}$ star. We compare hydrostatic and hydrodynamic models and test for different energies and widths of the depositing region. We find that due to the deposited energy, the envelope expands significantly, and under certain conditions, such as assuming a uniform electron scattering opacity, this energy input becomes sufficient to unbind material from the outer envelope. This, in turn, leads to the formation of an outflow. We find that higher deposited energy triggers a strong outflow and results in a somewhat hotter and less expanded envelope due to the rapid loss of energy through expelled material. This driving mechanism leads to sudden envelope expansion and the formation of strong outflows in our models, highlighting the generic hydrodynamic response of massive star envelopes to impulsive energy input.