Competition between gravity waves excited by convection and tides in stars that host a companion

TL;DR

This study models and compares the energy and angular momentum transport by gravity waves excited by convection and tides in stars with companions, revealing conditions under which each mechanism dominates.

Contribution

It provides a quantitative analysis of the relative importance of convection- and tide-excited gravity waves across different stellar and companion parameters.

Findings

Stochastic convection-driven waves dominate over tidal waves for Jupiter-mass companions.

Tidal excitation becomes significant only for close-in companions around late-type stars.

Presence of a companion does not significantly affect internal angular momentum transport in most cases.

Abstract

Asteroseismology has become a powerful tool in stellar astrophysics, offering unprecedented insights into the internal structures and dynamics of stars. It enables precise characterization of stellar interiors across a wide range of stellar masses and of evolutionary phases, from the main sequence to the white dwarf phase. At the same time, the number of detected close stellar and planetary companions throughout the entire stellar evolutionary phases has increased significantly, prompting key questions about the interplay between stellar evolution and binarity. We investigate the competition between gravity waves (IGW) excited by internal convection and those excited by tides in stars that host a companion. By modelling the energy and angular momentum luminosities transported by IGWs stochastically excited by convection and by tides, we seek to quantify their relative contributions and identify the key parameters that govern their efficiency. We compute the energy and angular momentum luminosities transported by both types of waves for a range of stellar masses and evolutionary stages, with a particular focus on understanding how the presence of a companion influences the angular momentum transport of the radiative layers of the host star. The competition between the two excitation mechanisms is sensitive to the mass and orbital properties of the companion, as well as the internal structure of the host star. We find that for a Jupiter-mass companion, the stochastic excitation dominates over tidal excitation during all evolutionary phases. Only for close-in stellar companions around late-type stars does the tidal excitation become more efficient. The presence of a companion is unlikely to significantly alter the internal angular momentum transport in the radiative layers of the host star, simplifying the modelling of IGW-driven angular momentum transport in stars that host a companion.