How do External Companions Affect Spin-Orbit Misalignment of Hot Jupiters?

TL;DR

This paper develops an analytic method to quantify how inclined distant companions influence the spin-orbit misalignment of hot Jupiters and applies it to observed systems, enhancing understanding of their dynamical histories.

Contribution

It introduces a simple, quantitative approach to evaluate the impact of external companions on spin-orbit misalignments in exoplanetary systems.

Findings

Provides a formula to assess external companions' influence on misalignment.

Applied to hot Jupiter systems with observed misalignments.

Extends methodology to multi-planet systems like Kepler-56.

Abstract

Consider a planet with its orbital angular momentum axis aligned with the spin axis of its host star. To what extent does an inclined distant companion (giant planet or binary star) affect this alignment? We provide an analytic, quantitative answer and apply it to hot Jupiter systems, for which misalignments between the orbital axis and the stellar spin axis have been detected. We also show how similar consideration can be applied to multi-planet systems with distant companions (such as Kepler-56). The result of this paper provides a simple method to assess the dynamical role played by external companions on spin-orbit misalignments in exoplanetary systems.