The True Stellar Obliquity of a Sub-Saturn Planet from the Tierras Observatory and KPF

2025/05/06 by Tamburo, Patrick, Yee, Samuel W., García-Mejía, Juliana +7 · 1 voice
#Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences

paper · doi:10.48550/arxiv.2505.03628

Abstract

We measure the true obliquity of TOI-2364, a K dwarf with a sub-Saturn-mass (M_p = 0.18 M_J) transiting planet on the upper edge of the hot Neptune desert. We used new Rossiter-McLaughlin observations gathered with the Keck Planet Finder to measure the sky-projected obliquity λ= 7^∘^{+10^∘}_-11^∘. Combined with a stellar rotation period of 23.47±0.29 days measured with photometry from the Tierras Observatory, this yields a stellar inclination of 90^∘ ± 13^∘ and a true obliquity ψ= 15.6^∘^{+7.7^∘}_-7.3^∘, indicating that the planet's orbit is well aligned with the rotation axis of its host star. The determination of ψ is important for investigating a potential bimodality in the orbits of short-period sub-Saturns around cool stars, which tend to be either aligned with or perpendicular to their host stars' spin axes.

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• arxiv.org/abs/2505.03628 🪐🔭 [bsky, 10 points, 0 comments]

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