Stellar Obliquity of the Ultra-short-period Planet System HD 93963

Stellar Obliquity of the Ultra-short-period Planet System HD 93963

We report an observation of the Rossiter–McLaughlin (RM) effect of the transiting planet HD 93963 Ac, a mini-Neptune planet orbiting a G0-type star with an orbital period of P _c  = 3.65 days, accompanied by an inner super-Earth planet with P _b  = 1.04 days. We observed a full transit of planet c o...

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Main Authors: Huan-Yu Teng, Fei Dai, Andrew W. Howard, Samuel Halverson, Howard Isaacson, Eiichiro Kokubo, Ryan A. Rubenzahl, Benjamin Fulton, Aaron Householder, Jack Lubin, Steven Giacalone, Luke Handley, Judah Van Zandt, Erik A. Petigura, J. M. Joel Ong, Pranav Premnath, Haochuan Yu, Steven R. Gibson, Kodi Rider, Arpita Roy, Ashley Baker, Jerry Edelstein, Chris Smith, Josh Walawender, Byeong-Cheol Lee, Yu-Juan Liu, Joshua N. Winn
Format: Article
Language:English
Published: IOP Publishing 2025-01-01
Series:The Astronomical Journal
Subjects:
Exoplanets
Mini Neptunes
Super Earths
Exoplanet dynamics
Online Access:https://doi.org/10.3847/1538-3881/addab9
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Summary:We report an observation of the Rossiter–McLaughlin (RM) effect of the transiting planet HD 93963 Ac, a mini-Neptune planet orbiting a G0-type star with an orbital period of P _c  = 3.65 days, accompanied by an inner super-Earth planet with P _b  = 1.04 days. We observed a full transit of planet c on 2024 May 3 UT with the Keck/Keck Planet Finder. The observed RM effect has an amplitude of ∼1 m s ^−1 and implies a sky-projected obliquity of $\lambda =1{4}_{-19}^{+17}$ degrees for HD 93963 Ac. Our dynamical analysis suggests that the two inner planets are likely well aligned with the stellar spin, to within a few degrees, thus allowing both to transit. Along with WASP-47, 55 Cnc, and HD 3167, HD 93963 is the fourth planetary system with an ultrashort-period planet and obliquity measurement(s) of any planet(s) in the system. HD 93963, WASP-47, and 55 Cnc favor largely coplanar orbital architectures, whereas HD 3167 has been reported to have a large mutual inclination (∼100°) between its transiting planets b and c. In this configuration, the probability that both planets transit is low. Moreover, one planet would quickly evolve to be nontransiting due to nodal precession. Future missions such as ESO/PLATO should detect the resulting transit duration variations. We encourage additional obliquity measurements of the HD 3167 system to better constrain its orbital architecture.
ISSN:1538-3881

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