Constraining the Planetary Obliquity Distribution of Warm Jupiters

Abstract

Warm Jupiters are an intriguing class of planets with uncertain origins. Their planetary obliquities could help distinguish between different formation pathways: planet-planet scattering and migration across resonances can excite large obliquities, whereas in-situ formation would more naturally produce low obliquities. We searched for oblateness-related anomalies in the transit light curves of six observationally favorable warm Jupiters: TOI-201b, TOI-1670c, TOI-199b, Kepler-9c, Kepler-30c, and Kepler-553c. Each planet's light curve is consistent with a spherical planet and provides degenerate constraints on the planet's sky-projected oblateness and obliquity. To overcome these limitations, we performed hierarchical Bayesian modeling of the population-level obliquity distribution. Assuming warm Jupiters are as oblate as Saturn ($f \approx 0.1$), we find their median obliquity to be below $12^\circ$ with $90$% confidence and below Saturn's obliquity ($27^\circ$) with $93$% confidence. Jupiter-like oblateness ($f \approx 0.06$) and larger obliquities are allowed. Simulations of JWST observations predict that significantly tighter constraints can be derived.