Hot Jupiter formation in stellar binaries
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A major focus of my research is on the formation/migration mechanisms of hot Jupiters. Despite the fact that hot Jupiters were the first type of exoplanet to be discovered around a main-sequence star, their existence continues to be a puzzle. It is widely thought that such planets cannot form at their observed orbital locations, and must instead have migrated from farther out. Competing theories of orbital migration for hot Jupiters exist, and a primary goal of my research is to help distinguish between various proposed migration theories.
In collaboration with Natalia Storch and Dong Lai, my work has focused on planets in stellar binaries, in which extreme eccentricity and inclination variations in a planetary orbit can arise, due to secular perturbations by a stellar companion (through Lidov-Kozai cycles). When the planet passes close to the star, the stellar spin axis can undergo chaotic evolution, as identified in work led by Natalia Storch (Storch, Anderson, & Lai 2014).
Lidov-Kozai cycles, combined with spin-orbit coupling and tidal dissipation can result in a hot Jupiter with an orbital plane significant misaligned with the stellar equator. Such spin-orbit misalignment is observed in many hot Jupiter systems, and can thus serve as a clue of the planet's migration history.
We have conducted an extensive population synthesis of hot Jupiter formation in stellar binaries (Anderson, Storch, & Lai 2016), taking into account the spin-orbit coupling between the star and planet and spin-down of the host star due to magnetic braking. We present distributions of spin-orbit misalignment angles for various properties of the planet, host star, and binary companion.
Obliquities of hot Jupiters orbiting a G-type star produced by Lidov-Kozai cycles from a stellar companion. We show results for different combinations of planet mass and planetary tidal dissipation strength. See Anderson, Storch, & Lai 2016 for more details.
Same as left, but showing results for hot Jupiters orbiting an F-type star.
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