Single-Star Warm-Jupiter Systems Tend to Be Aligned, Even Around Hot Stellar Hosts: No $T_{rm eff}-λ$ Dependency

Kavli Affiliate: George R. Ricker

| First 5 Authors: Xian-Yu Wang, Malena Rice, Songhu Wang, Shubham Kanodia, Fei Dai

| Summary:

The stellar obliquity distribution of warm-Jupiter systems is crucial for
constraining the dynamical history of Jovian exoplanets, as the warm Jupiters’
tidal detachment likely preserves their primordial obliquity. However, the
sample size of warm-Jupiter systems with measured stellar obliquities has
historically been limited compared to that of hot Jupiters, particularly in
hot-star systems. In this work, we present newly obtained sky-projected stellar
obliquity measurements for warm-Jupiter systems, TOI-559, TOI-2025, TOI-2031,
TOI-2485, TOI-2524, and TOI-3972, derived from the Rossiter-McLaughlin effect,
and show that all six systems display alignment with a median measurement
uncertainty of 13 degrees. Combining these new measurements with the set of
previously reported stellar obliquity measurements, our analysis reveals that
single-star warm-Jupiter systems tend to be aligned, even around hot stellar
hosts. This alignment exhibits a 3.4-$sigma$ deviation from the $T_{rm
eff}-lambda$ dependency observed in hot-Jupiter systems, where planets around
cool stars tend to be aligned, while those orbiting hot stars show considerable
misalignment. The current distribution of spin-orbit measurements for Jovian
exoplanets indicates that misalignments are neither universal nor primordial
phenomena affecting all types of planets. The absence of misalignments in
single-star warm-Jupiter systems further implies that many hot Jupiters, by
contrast, have experienced a dynamically violent history.

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