Adiabatic Mass Loss and the Outcome of the Common Envelope Phase of Binary Evolution

TL;DR

This paper introduces a new method for modeling common envelope events in binary star evolution, accounting for the donor star's structural response to mass loss, leading to more accurate predictions of remnant masses and orbital separations.

Contribution

The authors develop a self-consistent approach to determine remnant core masses during CE events, improving upon previous models that used fixed remnant assumptions.

Findings

Remnant core mass can be up to 30% larger than the He-core mass.

Method results in broader remnant mass and orbital separation distributions.

20% increase in CE survival rates compared to previous models.

Abstract

We have developed a new method for calculating common envelope (CE) events based on explicit consideration of the donor star's structural response to adiabatic mass loss. In contrast to existing CE prescriptions, which specify a priori the donor's remnant mass, we determine this quantity self-consistently and find it depends on binary and CE parameters. This aspect of our model is particularly important to realistic modeling for upper main sequence star donors without strongly degenerate cores (and hence without a clear core/envelope boundary). We illustrate the central features of our method by considering CE events involving 10 solar mass donors on or before their red giant branch. For such donors, the remnant core mass can be as much as 30% larger than the star's He-core mass. Applied across a population of such binaries, our methodology results in a significantly broader remnant mass and final orbital separation distribution and a 20% increase in CE survival rates as compared to previous prescriptions for the CE phase.