The Effect of Stellar Evolution on Migrating Warm Jupiters

TL;DR

This paper investigates how stellar evolution influences the migration and depletion of warm Jupiters through Kozai-Lidov oscillations, explaining their observed scarcity around larger stars.

Contribution

It introduces numerical simulations linking stellar evolution, Kozai-Lidov oscillations, and planetary migration, providing insights into warm Jupiter population dynamics.

Findings

Kozai-Lidov oscillations cause early planetary removal during stellar evolution.

Simulations show a relationship between periapse distance and migration rate.

Observed eccentricity distribution may be affected by observational biases.

Abstract

Warm jupiters are an unexpected population of extrasolar planets that are too near to their host to have formed in situ, but distant enough to retain a significant eccentricity in the face of tidal damping. These planets are curiously absent around stars larger than two solar radii. We hypothesize that the warm jupiters are migrating due to Kozai-Lidov oscillations, which leads to transient episodes of high eccentricity and a consequent tidal decay. As their host evolves, such planets would be rapidly dragged in or engulfed at minimum periapse, leading to a rapid depletion of the population with increasing stellar radius, as is observed. Using numerical simulations, we determine the relationship between periapse distance and orbital migration rate for planets 0.1 to 10 Jupiter masses and with orbital periods between 10 and 100 days. We find that Kozai-Lidov oscillations effectively result in planetary removal early in the evolution of the host star, possibly accounting for the observed deficit. While the observed eccentricity distribution is inconsistent with the simulated distribution for an oscillating and migrating warm jupiter population, observational biases may explain the discrepancy.