Empirical Tidal Dissipation in Exoplanet Hosts From Tidal Spin-Up

TL;DR

This study analyzes a large sample of hot Jupiter systems to empirically measure how stellar tidal dissipation varies with forcing frequency, revealing a sharp increase in the dissipation parameter that impacts planetary orbital evolution.

Contribution

It provides the first comprehensive empirical evidence that stellar tidal dissipation parameter $Q_ ext{star}'$ increases sharply with forcing frequency in hot Jupiter systems.

Findings

$Q_ ext{star}'$ increases from $10^5$ to $10^7$ as frequency rises.

The frequency dependence helps reconcile different tidal dissipation studies.

Implications for hot Jupiter orbital decay and stellar obliquity damping.

Abstract

Stars with hot Jupiters tend to be rotating faster than other stars of the same age and mass. This trend has been attributed to tidal interactions between the star and planet. A constraint on the dissipation parameter $Q_\star'$ follows from the assumption that tides have managed to spin up the star to the observed rate within the age of the system. This technique was applied previously to HATS-18 and WASP-19. Here we analyze the sample of all 188 known hot Jupiters with an orbital period $< 3.5$ days and a "cool" host star ($T_{eff} < 6100$ K). We find evidence that the tidal dissipation parameter ($Q_\star'$) increases sharply with forcing frequency, from $10^5$ at 0.5 day$^{-1}$ to $10^7$ at 2 day$^{-1}$. This helps to resolve a number of apparent discrepancies between studies of tidal dissipation in binary stars, hot Jupiters, and warm Jupiters. It may also allow for a hot Jupiter to damp the obliquity of its host star prior to being destroyed by tidal decay.