Evolving Low- and Intermediate-Mass Binaries: Departures from Classical Theory

TL;DR

This review examines recent developments in the understanding of low- and intermediate-mass binary star evolution, highlighting mechanisms that challenge classical theories and proposing new perspectives for future research.

Contribution

It critically reassesses classical models of binary evolution, incorporating recent hydrodynamical simulations and exploring mechanisms affecting orbital eccentricity and mass transfer.

Findings

Deviations from classical Roche lobe formalism in eccentric systems

Recent hydrodynamical simulations inform mass transfer models

Mechanisms for sustaining orbital eccentricity are identified

Abstract

This review explores the physical mechanisms driving the evolution of low- and intermediate-mass binary star systems, with particular emphasis on emerging mechanisms that challenge classical paradigms. We begin by describing the principal formation channels and orbital properties of binary systems. A critical reassessment of the Roche lobe formalism is presented, focusing on systems with eccentric orbits and asynchronous rotation, where deviations from traditional approximations become significant. We then review current theoretical models of mass and angular momentum exchange via Roche-lobe overflow, incorporating results from recent hydrodynamical simulations of wind accretion. The review also reports advances in tidal dissipation theory. Finally, we explore mechanisms capable of sustaining or exciting orbital eccentricity, including perturbations induced by mass transfer and interactions with circumbinary disks. These discussions aim to outline underexplored facets of binary evolution, offering new perspectives for theoretical and observational studies.