Testing the Origin of Hot Jupiters with Atmospheric Surveys

TL;DR

This paper explores the origins of hot Jupiters by analyzing atmospheric signatures, especially water abundance, to distinguish between high-eccentricity migration and in situ formation, using upcoming atmospheric data from the Ariel mission.

Contribution

It introduces a novel approach to test hot Jupiter formation theories through atmospheric composition, focusing on post-formation pollution signatures and their dependence on accretion mechanisms.

Findings

Water abundance in hot Jupiters can be significantly elevated if formed via high-eccentricity migration.

Observable pollution signatures are only detectable under pebble accretion in metal-rich disks.

Future atmospheric surveys can differentiate formation pathways by comparing hot Jupiters with wide-orbit planets.

Abstract

In spite of their long detection history, the origin of hot Jupiters remains to be resolved. While multiple dynamical evidence suggests high-eccentricity migration is most likely, conflicts remain when considering hot Jupiters as a population in the context of warm and cold Jupiters. Here, we turn to atmospheric signatures as an alternative mean to test the origin theory of hot Jupiters, focusing on population level trends that arise from post-formation pollution, motivated by the upcoming Ariel space mission whose goal is to deliver a uniform sample of exoplanet atmospheric constraints. We experiment with post-formation pollution by planetesimal accretion, pebble accretion, and disk-induced migration and find that an observable signature of post-formation pollution is only possible under pebble accretion in metal-heavy disks. If most hot Jupiters arrive at their present orbit by high-eccentricity migration while warm Jupiters emerge largely in situ, we expect the atmospheric water abundance of hot Jupiters to be significantly elevated compared to warm Jupiters. We report on the detectability of such signatures and further provide suggestions for future comparative atmospheric characterization between hot Jupiters and wide-orbit directly imaged planets to elucidate the properties of the dust substructures in protoplanetary disks.