Observational and Dynamical Constraints on High-eccentricity Migration of Hot and Warm Jupiters
Open Access
- Author:
- Jackson, Jonathan
- Graduate Program:
- Astronomy and Astrophysics
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 02, 2022
- Committee Members:
- Rebekah Dawson, Chair & Dissertation Advisor
Jason Wright, Major Field Member
James Kasting, Outside Unit & Field Member
Caryl Gronwall, Major Field Member
Rebekah Dawson, Program Head/Chair
Eric Ford, Major & Minor Field Member - Keywords:
- exoplanets
planet formation
hot Jupiters - Abstract:
- The discovery of the first exoplanets was accompanied by many new questions about planet formation and evolution. Among the first and most puzzling of these questions was how to account for the unexpected presence of hot Jupiters. Today, there are three prevailing categories of theories to explain their presence: in situ formation, disk migration, and high-eccentricity migration. It remains unclear which of these processes constitutes the dominant channel of hot Jupiter delivery. I study the latter theory here, in which a Jupiter-sized planet is formed on a long period orbit, excited to an extreme eccentricity, and pulled inwards through tidal circularization. I present results that constrain the likelihood of this channel producing a large fraction of the observed hot Jupiters through three different approaches, all of which utilize observations of warm Jupiters, a more temperate population of giant planets that may be precursors to hot Jupiters. First, I conduct a case study of a highly eccentric warm Jupiter, Kepler-419b, which has a known eccentric, coplanar companion. Despite being an ostensibly strong candidate for high-eccentricity migration, in its current orbital configuration, Kepler-419b cannot be undergoing tidal circularization. I conduct a series of N-body simulations and find that an additional companion in a narrow region of parameter space could produce strong enough eccentricity oscillations to reach the high-eccentricity migration threshold. I also show that such a companion could remain hidden in the current observations of the system. Next, I approach the problem from a population perspective. If warm Jupiters are engaging in high-eccentricity migration, they require massive, nearby companions to exchange angular momentum with. I calculate the detectability of this necessary population of companions and show that it could have remained hidden in the Kepler sample, but should be largely detectable with radial velocity and astrometric follow up of TESS warm Jupiters. If this population is found not to exist, another theory is needed to explain the observed warm Jupiters. Lastly, I conduct a statistical analysis of the Kepler warm Jupiter population. If high-eccentricity migration is a common delivery mechanism for hot Jupiters, we would expect to observe some super-eccentric Jupiters with Kepler, of which we find none. I quantify the statistical significance of this dearth of super-eccentric planets and set an upper limit of 62%$on the fraction of hot Jupiters that can be explained by high-eccentricity migration.