Revisiting Common Envelope Evolution -- A New Semi-Analytic Model for N-body and Population Synthesis Codes

TL;DR

This paper introduces a semi-analytic model for common envelope evolution in binary systems that accounts for eccentricity and aligns with hydrodynamical simulations, improving population synthesis and N-body simulations.

Contribution

The authors develop a novel semi-analytic formalism for modeling common envelope evolution that incorporates eccentricity and can be integrated into population synthesis and N-body codes.

Findings

Model results are consistent with hydrodynamical simulations.

Final eccentricity distribution matches observed post-common-envelope binaries.

Applicable to both population synthesis and star cluster simulations.

Abstract

We present a novel way of modeling common envelope evolution in binary and few-body systems. We consider the common envelope inspiral as driven by a drag force with a power-law dependence in relative distance and velocity. The orbital motion is resolved either by direct N-body integration or by solving the set of differential equations for the orbital elements as derived using perturbation theory. Our formalism can model the eccentricity during the common envelope inspiral, and it gives results consistent with smoothed particles hydrodynamical simulations. We apply our formalism to common envelope events from binary population synthesis models and find that the final eccentricity distribution resembles the observed distribution of post-common-envelope binaries. Our model can be used for time-resolved common-envelope evolution in population synthesis calculations or as part of binary interactions in direct N-body simulations of star clusters.