A Homogeneous Catalog of Rossiter-McLaughlin Systems: Distinct $e$-$λ$ Trends in Three Gas-Giant Mass Regimes

Xian-Yu Wang; Songhu Wang; Konstantin Batygin

doi:10.3847/2041-8213/ae907d

paper

A Homogeneous Catalog of Rossiter-McLaughlin Systems: Distinct $e$ - $λ$ Trends in Three Gas-Giant Mass Regimes

arXiv:2605.28719 · doi:10.3847/2041-8213/ae907d

Abstract

Stellar obliquity ( $λ$ ) and orbital eccentricity ( $e$ ) trace the dynamical histories of close-in giant planets, but the current observational picture is assembled from heterogeneous analyses that have obscured population-level trends. In this work, we homogeneously refit systems with Rossiter-McLaughlin (RM) measurements by performing a joint global fit to spectral energy distributions, transit light curves, mid-transit times, out-of-transit and in-transit radial velocities, yielding self-consistent posterior distributions for the physical and orbital parameters of both stars and planets across 256 systems. Restricting to 146 single-star systems with reliable planet-mass measurements, we uncover pronounced structure in the $e - λ$ plane that depends on planet mass: (i) sub-Saturns ( $M_{p} \leq\sim 0.3 M_{J}$ ) can be both eccentric and misaligned; (ii) Jupiters ( $\sim 0.3 M_{J} < M_{p} \leq\sim 3 M_{J}$ ) are misaligned only on circular orbits; and (iii) super Jupiters and brown dwarfs ( $M_{p} >\sim 3 M_{J}$ ) are aligned across the full eccentricity range. A two-dimensional Kolmogorov-Smirnov test shows that the joint $(e, λ)$ distributions differ significantly among these three mass regimes. These trends demonstrate that $λ$ depends jointly on eccentricity and planet mass, implying that obliquity alone is not a unique tracer of evolutionary history and underscoring the need for a unified framework for the origins of spin-orbit misalignment. The full catalog from this work is publicly available at https://www.stellarobliquity.com .

arXiv comment24 pages, 2 figures, accepted for publication in ApJL. For an online database including the catalog and plots, see https://www.stellarobliquity.com

A Homogeneous Catalog of Rossiter-McLaughlin Systems: Distinct e-λ Trends in Three Gas-Giant Mass Regimes

Abstract

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A Homogeneous Catalog of Rossiter-McLaughlin Systems: Distinct $e$ - $λ$ Trends in Three Gas-Giant Mass Regimes