Tidal Wave Breaking in the Eccentric Lead-In to Mass Transfer and Common Envelope Phases

TL;DR

This paper investigates how tidal wave breaking during eccentric close passages in binary star systems leads to mass loss and influences their evolution, including circularization or runaway mass transfer.

Contribution

It introduces a detailed model of tidal wave breaking and its effects on mass loss and orbital evolution in eccentric binary systems.

Findings

Wave breaking causes shock-heated atmospheres around stars.

Mass ratio determines whether systems undergo circularization or runaway mass transfer.

Nonlinear dissipation influences the evolutionary outcome of binary systems.

Abstract

The evolution of many close binary and multiple star systems is defined by phases of mass exchange and interaction. As these systems evolve into contact, tidal dissipation is not always sufficient to bring them into circular, synchronous orbits. In these cases, encounters of increasing strength occur while the orbit remains eccentric. This paper focuses on the outcomes of close tidal passages in eccentric orbits. Close eccentric passages excite dynamical oscillations about the stars' equilibrium configurations. These tidal oscillations arise from the transfer of orbital energy into oscillation mode energy. When these oscillations reach sufficient amplitude, they break near the stellar surface. The surface wave-breaking layer forms a shock-heated atmosphere that surrounds the object. The continuing oscillations in the star's interior launch shocks that dissipate into the this atmosphere, damping the tidal oscillations. We show that the rapid, nonlinear dissipation associated with the wave breaking of fundamental oscillation modes therefore comes with coupled mass loss to the wave breaking atmosphere. The mass ratio is an important characteristic that defines the relative importance of mass loss and energy dissipation and therefore determines the fate of systems evolving under the influence of nonlinear dissipation. The outcome can be rapid tidal circularization ($q\ll1$) or runaway mass exchange ($q\gg1$).