Explaining Common Envelope Evolution and Dynamics in binary stellar systems

Introduction

A thorough understanding of stellar evolution is key to nearly any branch of astrophysics. The majority of stars evolve in binary or multiple systems, and interactions often occur between their components. Such dynamical interaction phases are pivotal for the fate of the system and its constituents, but they elude classical stellar modeling.

Common-Envelope Phases

Common-envelope phases, in which a compact companion spirals into the envelope of a giant primary star, are the glaring gaps in our knowledge and pose one of the last unsolved fundamental problems in stellar astrophysics.

ExCEED Project Overview

The ExCEED project breaks new ground by developing a strategy to reach a comprehensive understanding of common-envelope evolution. It combines:

1. Leading three-dimensional magnetohydrodynamic moving-mesh simulations
2. Innovative models of physical processes

These elements work together to decipher the dynamical interaction between the stellar cores and the envelope material.

Post-Common Envelope Evolution

On this basis, the post-common envelope evolution is explored by consistently linking to classical one-dimensional models. Predictions for astronomical observables are derived, and a faithful effective prescription for representing common-envelope phases in binary stellar evolution and population synthesis calculations is constructed.

Implications of the ExCEED Project

The new understanding of common-envelope evolution provided by the ExCEED project marks a breakthrough in stellar astrophysics and has implications beyond this field. ExCEED finally settles the long-standing questions of:

• The mechanism of envelope ejection
• The orbital separation of the post-common envelope remnant binary system

This understanding allows us to comprehend the formation of the targets of gravitational-wave astronomy, which holds promise to solve problems of fundamental physics, the progenitors of Type Ia supernovae, and many other astrophysical events.