# Formation of Hot Jupiters through Secular Chaos and Dynamical Tides

## TL;DR

This paper investigates how secular chaos combined with dynamical tides can lead to the formation of hot Jupiters through high-eccentricity migration, highlighting the process's efficiency and limitations.

## Contribution

It introduces a detailed model including dynamical tides in secular chaos-driven migration, showing their role in hot Jupiter formation and resulting orbital properties.

## Key findings

- Dynamical tides facilitate hot Jupiter formation by preventing tidal disruption.
- Final orbital periods are typically 2-3 days, shorter than observed.
- The model predicts fewer retrograde hot Jupiters than observed.

## Abstract

The population of giant planets on short-period orbits can potentially be explained by some flavours of high-eccentricity migration. In this paper we investigate one such mechanism involving "secular chaos", in which secular interactions between at least three giant planets push the inner planet to a highly eccentric orbit, followed by tidal circularization and orbital decay. In addition to the equilibrium tidal friction, we incorporate dissipation due to dynamical tides that are excited inside the giant planet. Using the method of Gaussian rings to account for planet-planet interactions, we explore the conditions for extreme eccentricity excitation via secular chaos and the properties of hot Jupiters formed in this migration channel. Our calculations show that once the inner planet reaches a sufficiently large eccentricity, dynamical tides quickly dissipate the orbital energy, producing an eccentric warm Jupiter, which then decays in semi-major axis through equilibrium tides to become a hot Jupiter. Dynamical tides help the planet avoid tidal disruption, increasing the chance of forming a hot Jupiter, although not all planets survive the process. We find that the final orbital periods generally lie in the range of 2-3 days, somewhat shorter than those of the observed hot Jupiter population. We couple the planet migration to the stellar spin evolution to predict the final spin-orbit misalignments. The distribution of the misalignment angles we obtain shows a lack of retrograde orbits compared to observations. Our results suggest that high-eccentricity migration via secular chaos can only account for a fraction of the observed hot Jupiter population.