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

TL;DR

This study models how stellar rotation and tidal dissipation influence the orbital evolution of close-in planets around low-mass stars, revealing that stellar tides significantly affect planetary migration, especially during the pre-main sequence phase.

Contribution

It presents the first comprehensive model coupling stellar structure, rotation, and tidal dissipation to study close-in planet dynamics around low-mass stars.

Findings

Tidal friction from stellar dynamical tides can exceed equilibrium tides by several orders of magnitude.

Planetary orbital migration is more pronounced and depends on stellar mass, rotation, and age.

Habitable zone planets are weakly affected by stellar tides due to long migration timescales.

Abstract

Since twenty years, a large population of close-in planets orbiting various classes of low-mass stars (from M to A-type stars) has been discovered. In such systems, the dissipation of the kinetic energy of tidal flows in the host star may modify its rotational evolution and shape the orbital architecture of the surrounding planetary system. In this context, recent works demonstrated that the amplitude of this dissipation can vary over several orders of magnitude as a function of stellar mass, age and rotation. In addition, the stellar rotation evolution strongly impacts angular momentum exchanges within star-planet systems. Therefore, it is now necessary to take into account the structural and rotational evolution of stars when studying the orbital evolution of close-in planets. The presence of planets may also modify the rotation of the host stars and as a consequence their evolution, magnetic activity and mixing. In this work, we present the first study of the dynamics of close-in planets of various masses orbiting low-mass stars (from $0.6$ to $1.2~M_\star$) where we compute the simultaneous evolution of the star's structure, rotation and tidal dissipation in its external convective enveloppe. We find that tidal friction due to the stellar dynamical tide, i.e. tidal inertial waves excited in the convection zone, can be larger by several orders of magnitude than the one of the equilibrium tide, especially during the PMS phase. Consequently, the orbital migration of the planet is now more pronounced and depends more on the stellar mass, rotation and age. This would very weakly affect the planets in the habitable zone because they are located at orbital distances such that stellar tide-induced migration happens on very long timescales. We also demonstrate that the rotational evolution of host stars is only weakly affected by the presence of planets except for massive companions.