Tidal dissipation in evolving low-mass and solar-type stars with predictions for planetary orbital decay

TL;DR

This paper models tidal dissipation in low-mass and solar-type stars throughout their evolution, highlighting the dominant mechanisms for binary and planetary orbital evolution, and providing predictions for observable effects like transit timing shifts.

Contribution

It introduces a comprehensive, frequency-dependent model of tidal dissipation in stars, including inertial and gravity waves, improving upon previous simplified approaches.

Findings

Inertial wave dissipation dominates binary star synchronization.

Gravity wave damping predicts hot Jupiter destruction, not Earth-mass planets.

Revised dissipation estimates refine stellar tidal quality factors.

Abstract

We study tidal dissipation in stars with masses in the range $0.1-1.6 M_\odot$ throughout their evolution, including turbulent effective viscosity acting on equilibrium tides and inertial waves in convection zones, and internal gravity waves in radiation zones. We consider a range of stellar evolutionary models and incorporate the frequency-dependent effective viscosity acting on equilibrium tides based on the latest simulations. We compare the tidal flow and dissipation obtained with the conventional equilibrium tide, which is strictly invalid in convection zones, finding that the latter typically over-predicts the dissipation by a factor of 2-3. Dissipation of inertial waves is computed using a frequency-averaged formalism accounting for realistic stellar structure for the first time, and is the dominant mechanism for binary circularization and synchronization on the main sequence. Dissipation of gravity waves in the radiation zone assumes these waves to be fully damped (e.g.~by wave breaking), and is the dominant mechanism for planetary orbital decay. We calculate the critical planetary mass required for wave breaking as a function of stellar mass and age, and show that this mechanism predicts destruction of many hot Jupiters but probably not Earth-mass planets on the main sequence. We apply our results to compute tidal quality factors following stellar evolution, and tidal evolutionary timescales, for the orbital decay of hot Jupiters, and the spin synchronization and circularization of binary stars. We also provide predictions for shifts in transit arrival times due to tidally-driven orbital decay of hot Jupiters that may be detected with NGTS, TESS or PLATO.