The variation of the tidal quality factor of convective envelopes of rotating low-mass stars along their evolution

TL;DR

This paper models how the tidal quality factor of convective envelopes in low-mass stars varies throughout their evolution, affecting tidal dissipation and orbital dynamics of exoplanets.

Contribution

It introduces an analytical method to compute the frequency-averaged tidal dissipation in stellar convective envelopes across stellar evolution stages.

Findings

Tidal quality factor decreases during Pre-Main-Sequence for fixed rotation.

Minimum dissipation occurs around 0.6 solar masses on the Main Sequence.

Rotational evolution enhances tidal dissipation in early stellar phases.

Abstract

More than 1500 exoplanets have been discovered around a large diversity of host stars (from M- to A-type stars). Tidal dissipation in their convective envelope is a key actor that shapes the orbital architecture of short-period systems and that still remains unknown. Using a simplified two-layer assumption and grids of stellar models, we compute analytically an equivalent modified tidal quality factor, which is proportional to the inverse of the frequency-averaged dissipation due to the viscous friction applied by turbulent convection on tidal waves. It leads the conversion of their kinetic energy into heat and tidal evolution of orbits and spin. During their Pre-Main-Sequence, all low-mass stars have a decrease of the equivalent modified tidal quality factor for a fixed angular velocity of their convective envelope. Next, it evolves on the Main Sequence to an asymptotic value that is minimum for $0.6M_{\odot}$ K-type stars and that increases by several orders of magnitude with increasing stellar mass. Finally, the rotational evolution of low-mass stars strengthens tidal dissipation during the Pre-Main-Sequence.