Dynamical tides excited in rotating stars of different masses and ages and the formation of close in orbits

TL;DR

This study investigates how dynamical tides in rotating stars of various masses and ages influence the formation of close-in exoplanets and binary systems, highlighting the weaker interactions in more massive stars and the impact of stellar evolution.

Contribution

It compares normal mode and numerical simulation approaches to evaluate tidal interactions across different stellar types and evolutionary stages, providing new insights into tidal effects on orbit circularization.

Findings

Tidal interactions are weaker in more massive stars due to less convective activity.

Retrograde orbits experience stronger tidal interactions than prograde ones.

Evolved stars exhibit increased tidal effects due to radial expansion.

Abstract

We study the tidal response of rotating solar mass stars, as well as more massive rotating stars, of different ages in the context of tidal captures leading to either giant exoplanets on close in orbits, or the formation of binary systems in star clusters. To do this, we adopt approaches based on normal mode and associated overlap integral evaluation, developed in a companion paper by Ivanov et al., and direct numerical simulation, to evaluate energy and angular momentum exchanges between the orbit and normal modes. The two approaches are found to be in essential agreement apart from when encounters occur near to pseudosynchronization, where the stellar angular velocity and the orbital angular velocity at periastron are approximately matched. We find that the strength of tidal interaction being expressed in dimensionless natural units is significantly weaker for the more massive stars, as compared to the solar mass stars, because of the lack of significant convective regions in the former case. On the other hand the interaction is found to be stronger for retrograde as opposed to prograde orbits in all cases. In addition, for a given pericentre distance, tidal interactions also strengthen for more evolved stars on account of their radial expansion. In agreement with previous work based on simplified polytropic models, we find that energy transferred to their central stars could play a significant role in the early stages of the circularisation of potential 'Hot Jupiters'.