Orbital evolution by dynamical tides in solar type stars

Application to binary stars and planetary orbits

Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands

Corresponding author: M. G. Witte, marnix@astro.uva.nl

Received: 18 September 2001
Accepted: 23 January 2002

Abstract

We study the tidal evolution of eccentric binary systems consisting of a solar type main sequence star accompanied by either another solar type star, or by a planet with a mass similar to Jupiter's mass. The tidal dissipation which takes place in the solar type star(s) is calculated in the framework of dynamical tides, and resonant interaction with the g-mode and quasi-toroidal oscillation eigenmodes of the stellar component(s) is included in the orbital calculations. It appears that in a system of two solar type stars intervals during which harmonic components of the perturbing tidal potential become locked onto resonances with stellar oscillation modes appear ubiquitously, significantly enhancing the efficiency of the tidal coupling. In our calculations stellar binaries become circularized during the main sequence lifetime for orbital periods up to about 10 days, or 16 days in the case of very slow stellar rotation. Efficient resonance locking causes significant tidal decay in weakly eccentric planetary binaries with orbital periods up to approximately 5 days in case the solar type star is a slow rotator, and very large increase of the orbital period and eccentricity in case the star is rotating rapidly. The dynamical tide with inclusion of the effects of close resonances with the stellar oscillation modes provides considerably more efficient tidal coupling than the equilibrium tide with viscous damping of turbulent eddies. stars: rotation – stars: oscillations – stars: binaries: close – planetary systems