Tidal Evolution of Close-in Exoplanets and Host Stars

TL;DR

This paper investigates how tidal interactions and magnetic braking influence the evolution of close-in exoplanets and their host stars, explaining observed distributions of orbital and stellar rotation periods.

Contribution

It presents a simulation-based analysis of tidal and magnetic braking effects, linking system evolution to observed period distributions and identifying key parameters like the relaxation factor.

Findings

Short-period hot Jupiters cluster around 25-day stellar rotation periods.

The evolution model explains irregularities in system distributions.

A relaxation factor of about 10 s^{-1} fits the observed data.

Abstract

The evolution of exoplanetary systems with a close-in planet is ruled by the tides mutually raised on the two bodies and by the magnetic braking of the host star. This paper deals with consequences of this evolution and some features that can be observed in the distribution of the systems two main periods: the orbital periods and the stars rotational periods. The results of the simulations are compared to plots showing both periods as determined from the light curves of a large number of Kepler objects of interest. These plots show important irregularities as a dearth of systems in some regions and accumulations of hot Jupiters in others. It is shown that the accumulation of short-period hot Jupiters around stars with rotation periods close to 25 days results from the evolution of the systems under the joint action of tides and braking, and requires a relaxation factor for solar-type stars of around $10 \, s^{-1}$.