Inflated Eccentric Migration of Evolving Gas Giants II – Numerical Methodology and Basic Concepts

Abstract

Hot and warm Jupiters (HJs&WJs) are gas-giant planets orbiting their host stars at short orbital periods, posing a challenge to their efficient in situ formation. Therefore, most HJs&WJs are thought to have migrated from an initially farther-out birth location. Current migration models, i.e., disk migration (gas-dissipation driven) and eccentric migration (tidal evolution driven), fail to produce the occurrence rate and orbital properties of HJs&WJs. Here we study the role of thermal evolution and its coupling to tidal evolution. We use AMUSE, a numerical environment, and MESA, planetary evolution modeling, to model in detail the coupled internal and orbital evolution of gas giants during their eccentric migration. In a companion paper, we use a simple semianalytic model, validated by our numerical model, and run a population-synthesis study. We consider the initially inflated radii of gas giants (expected following their formation), as well study the effects of the potentially slowed contraction and even reinflation of gas giants (due to tidal and radiative heating) on the eccentric migration. Tidal forces that drive eccentric migration are highly sensitive to the planetary structure and radius. Consequently, we find that this form of inflated eccentric migration operates on significantly (up to an order of magnitude) shorter timescales than previously studied eccentric-migration models. Therefore, inflated eccentric migration gives rise to the more rapid formation of HJs&WJs, higher occurrence rates of WJs, and higher rates of tidal disruptions, compared with previous eccentric-migration models that consider constant ∼Jupiter radii for HJ and WJ progenitors. Coupled thermal–dynamical evolution of eccentric gas giants can therefore play a key role in their evolution.