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

TL;DR

This study shows that single-star warm-Jupiter systems are generally aligned regardless of stellar temperature, challenging previous notions of a $T_{ m eff}- heta$ correlation seen in hot Jupiters, and suggesting different dynamical histories.

Contribution

The paper provides new stellar obliquity measurements for six warm-Jupiter systems and demonstrates their alignment, contrasting with hot-Jupiter systems and refining understanding of planetary dynamical evolution.

Findings

All six newly measured warm-Jupiter systems are aligned.

Warm-Jupiter systems show no $T_{ m eff}- heta$ dependency.

Misalignments are not universal and are likely not primordial.

Abstract

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.