Rapid binary star evolution for N-body simulations and population synthesis

Abstract

We present an algorithm for the rapid evolution of binary stars. It is based on simple fitting formulae for the evolution of single stars. Mass loss, mass transfer and common-envelope evolution are followed with the changes to both the mass donor and the accretor where applicable. We describe a procedure for integrating our formulae and give examples of how we can follow the evolution of Algols and cataclysmic variables. The algorithm can be used for simple binary population synthesis. We also explain how we incorporate it into N-body simulations where we introduce a new scheme that deals with colliding stars.