Calibration of Equilibrium Tide Theory for Extrasolar Planet Systems II

TL;DR

This paper provides an empirical calibration of equilibrium tidal theory for extrasolar planets, incorporating detailed models of planetary and stellar structures to better understand orbital evolution, spin-orbit alignment, and planet survival.

Contribution

It introduces a new calibration method for tidal interactions that accounts for internal structures, explaining observed spin-orbit alignments and short-period planet populations.

Findings

Stellar tides can reorient star spins without destroying planetary orbits.

Evidence for two processes influencing short-period planet populations.

Planet survival is heavily influenced by heat dissipation, risking orbital inflation.

Abstract

We present a new empirical calibration of equilibrium tidal theory for extrasolar planet systems, extending a prior study by incorporating detailed physical models for the internal structure of planets and host stars. The resulting strength of the stellar tide produces a coupling that is strong enough to reorient the spins of some host stars without causing catastrophic orbital evolution, thereby potentially explaining the observed trend in alignment between stellar spin and planetary orbital angular momentum. By isolating the sample whose spins should not have been altered in this model, we also show evidence for two different processes that contribute to the population of planets with short orbital periods. We apply our results to estimate the remaining lifetimes for short period planets, examine the survival of planets around evolving stars, and determine the limits for circularisation of planets with highly eccentric orbits. Our analysis suggests that the survival of circularised planets is strongly affected by the amount of heat dissipated, which is often large enough to lead to runaway orbital inflation and Roche lobe overflow.