Effect of the rotation, tidal dissipation history and metallicity of stars on the evolution of close-in planets

TL;DR

This study models the combined evolution of low-mass stars and their close-in planets, revealing that stellar tidal dissipation, especially during early phases, significantly influences planetary orbital evolution, with metallicity further affecting this process.

Contribution

It introduces a comprehensive model of star-planet tidal interactions considering stellar evolution, rotation, and metallicity, highlighting the dominant role of dynamical tides during the PMS phase.

Findings

Dynamical tides can be several orders of magnitude stronger than equilibrium tides.

High stellar dissipation during PMS significantly affects planetary semi-major axes.

Higher stellar metallicity leads to increased tidal dissipation and planetary migration.

Abstract

Since 1995, numerous close-in planets have been discovered around low-mass stars (M to A-type stars). These systems are susceptible to be tidally evolving, in particular the dissipation of the kinetic energy of tidal flows in the host star may modify its rotational evolution and also shape the orbital architecture of the surrounding planetary system. Recent theoretical studies have shown that the amplitude of the stellar dissipation can vary over several orders of magnitude as the star evolves, and that it also depends on the stellar mass and rotation. We present here one of the first studies of the dynamics of close-in planets orbiting low-mass stars (from $0.6~M_\odot$ to $1.2~M_\odot$) where we compute the simultaneous evolution of the star's structure, rotation and tidal dissipation in its external convective envelope. We demonstrate that tidal friction due to the stellar dynamical tide, i.e. tidal inertial waves (their restoring force is the Coriolis acceleration) excited in the convection zone, can be larger by several orders of magnitude than the one of the equilibrium tide currently used in celestial mechanics. This is particularly true during the Pre Main Sequence (PMS) phase and to a lesser extent during the Sub Giant (SG) phase. Numerical simulations show that only the high dissipation occurring during the PMS phase has a visible effect on the semi-major axis of close-in planets. We also investigate the effect of the metallicity of the star on the tidal evolution of planets. We find that the higher the metallicity of the star, the higher the dissipation and the larger the tidally-induced migration of the planet.