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

@misc{wang2026homogeneous,
  title = {{A Homogeneous Catalog of Rossiter-McLaughlin Systems: Distinct $e$-$λ$ Trends in Three Gas-Giant Mass Regimes}},
  author = {Xian-Yu Wang and Songhu Wang and Konstantin Batygin},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2605.28719},
  eprint = {2605.28719},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2605.28719},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - A Homogeneous Catalog of Rossiter-McLaughlin Systems: Distinct e-λ Trends in Three Gas-Giant Mass Regimes
AU  - Xian-Yu Wang
AU  - Songhu Wang
AU  - Konstantin Batygin
PY  - 2026
DA  - 2026/09/02
PB  - arXiv
DO  - 10.48550/arxiv.2605.28719
UR  - https://arxiv.org/abs/2605.28719
AB  - 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 ≤ ∼0.3M_J) can be both eccentric and misaligned; (ii) Jupiters (∼0.3M_J<M_p ≤ ∼3 M_J) are misaligned only on circular orbits; and (iii) super Jupiters and brown dwarfs (M_p>∼3M_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 .
ER  -