The Tale of a Hungry Subgiant and Its Brown Dwarf: Interior Radiative Damping Dominates the Tidal Evolution of TOI-5882

TL;DR

This paper introduces a comprehensive tidal evolution framework coupling binary evolution and linear tidal response, revealing radiative damping's dominance in the system's evolution and refining predictions of inspiral timescales.

Contribution

It presents a novel, self-consistent method combining MESA and GYRE-tides to accurately model tidal interactions, emphasizing the importance of dissipation mechanisms.

Findings

Interior radiative damping dominates tidal evolution in TOI-5882.

Classical models underestimate the star's angular momentum evolution by orders of magnitude.

The inspiral timescale is reduced by 2-6 times, accelerating companion inspiral by 25-110 Myr.

Abstract

We present a self-consistent tidal evolution framework that couples binary evolution from MESA to the full linear tidal response from GYRE-tides. Applying this framework to TOI-5882, a subgiant hosting a short-period brown dwarf, we show that interior radiative damping dominates the system's tidal evolution, with the classical equilibrium tidal model significantly underestimating the star's angular momentum evolution by several orders of magnitude. Consequently, our combined framework predicts a 2--6 fold reduction in the engulfment timescale, accelerating the companion's inspiral by roughly 25--110 Myr. By modeling angular momentum transport through the star as it evolves, we demonstrate that the early inspiral is driven by the non-resonant dissipation of internal gravity waves, before transitioning into a regime dominated by resonance crossings as the system approaches Roche-lobe overflow. We highlight the necessity of reframing the historical dichotomy between equilibrium and dynamical tides and instead propose categorizing tidal interactions around their dissipation mechanisms: radiatively and viscously damped tides. Our framework is broadly applicable to the tidal modeling of a wide class of star-companion systems, from binary stars to hot Jupiters, in a self-consistent and computationally feasible manner.