Revisiting Planetary Systems in Okayama Planet Search Program
Huan-Yu Teng, Fei Dai, Andrew Howard, Howard Isaacson, Ryan Rubenzahl, Isabel Angelo, Alex Polanski
November, 2024
Publication
Astronomical Journal
Abstract
We report the observation of the transiting planet TOI-942c, a Neptunian planet orbiting a young K-type star approximately 50 Myr years old. Using Keck/HIRES, we observed a partial transit of the planet and detected an associated radial velocity anomaly. By modeling the Rossiter-McLaughlin (RM) effect, we derived a sky-projected obliquity of |lambda|=24+14−14 degrees, indicating TOI-942c is in a prograde and likely aligned orbit. Upon incorporation of the star's inclination and the planet's orbital inclination, we determined a true obliquity for TOI-942c lower than 43 degrees at 84% confidence, while dynamic analysis strongly suggests TOI-942c is aligned with stellar spin and coplanar with the inner planet. Furthermore, TOI-942c is also a suitable target for studying atmospheric loss of young Neptunian planets that are likely still contracting from the heat of formation. We observed a blueshifted excess absorption in the H-alpha line at 6564.7 Ang, potentially indicating atmospheric loss due to photoevaporation. However, due to the lack of pre-ingress data, additional observations are needed to confirm this measurement.
[Teng et al. (2023, AJ)]