Inflated Eccentric Migration of Evolving Gas Giants I – Accelerated Formation and Destruction of Hot and Warm Jupiters

Abstract

Hot and warm Jupiters (HJs and WJs, correspondingly) are gas giants orbiting their host stars at very short orbital periods (P HJ < 10 days; 10 < P WJ < 200 days). HJs and a significant fraction of WJs are thought to have migrated from initially farther-out birth locations. While such migration processes have been extensively studied, the thermal evolution of gas giants and its coupling with migration processes are usually overlooked. In particular, gas giants end their core accretion phase with large radii, then contract slowly to their final radii. Moreover, intensive heating can slow the contraction at various evolutionary stages. The initial large inflated radii lead to faster tidal migration, due to the strong dependence of tides on the radius. Here, we explore this accelerated migration channel, which we term inflated eccentric migration, using a semi-analytical, self-consistent model of the thermal–dynamical evolution of the migrating gas giants, later validated by our numerical model (see the companion paper, paper II). We demonstrate our model for specific examples and carry out a population synthesis study. Our results provide a general picture of the properties of the formed HJs and WJs via inflated migration, and their dependence on the initial parameters/distributions. We show that the tidal migration of gas giants could occur much more rapidly then previously thought, and could lead to the accelerated destruction and formation of HJs and an enhanced formation rate for WJs. Accounting for the coupled thermal–dynamical evolution is therefore critical to understanding the formation of HJs/WJs, and the evolution and final properties of the population, and it plays a key role in their migration processes.