Long-period Jovian Tilts the Orbits of Two sub-Neptunes Relative to Stellar Spin Axis in Kepler-129
Abstract
We present the discovery of Kepler-129 d (P_d = 7.2_(-0.3)^(+0.4) yr, m sin i_d = 8.3_(-0.7)^(+1.1), M_(Jup), e_d = 0.15_(-0.05)^(+0.07)) based on six years of radial-velocity observations from Keck/HIRES. Kepler-129 also hosts two transiting sub-Neptunes: Kepler-129 b (P_b = 15.79 days, r_b = 2.40 ± 0.04 R_⊕) and Kepler-129 c (P_c = 82.20 days, r_c = 2.52 ± 0.07 R_⊕) for which we measure masses of m_b < 20 M_⊕ and m_c = 43₋₁₂⁺¹³ M_⊕. Kepler-129 is a hierarchical system consisting of two tightly packed inner planets and a massive external companion. In such a system, two inner planets precess around the orbital normal of the outer companion, causing their inclinations to oscillate with time. Based on an asteroseismic analysis of Kepler data, we find tentative evidence that Kepler-129 b and c are misaligned with stellar spin axis by ≳38°, which could be torqued by Kepler-129 d if it is inclined by ≳19° relative to inner planets. Using N-body simulations, we provide additional constraints on the mutual inclination between Kepler-129 d and inner planets by estimating the fraction of time during which two inner planets both transit. The probability that two planets both transit decreases as their misalignment with Kepler-129 d increases. We also find a more massive Kepler-129 c enables the two inner planets to become strongly coupled and more resistant to perturbations from Kepler-129 d. The unusually high mass of Kepler-129 c provides a valuable benchmark for both planetary dynamics and interior structure, since the best-fit mass is consistent with this 2.5 R_⊕ planet having a rocky surface.
Additional Information
© 2021. The American Astronomical Society. Received 2021 February 19; revised 2021 May 7; accepted 2021 May 26; published 2021 August 5. J.Z. would like to thank Daniel Fabrycky, Juliette Becker, Dong Lai, Johanna Teske, and Jerry Xuan for helpful discussions. L.M.W. is supported by the Beatrice Watson Parrent Fellowship and NASA ADAP Grant 80NSSC19K0597. D.H. acknowledges support from the Alfred P. Sloan Foundation, the National Aeronautics and Space Administration (80NSSC19K0597), and the National Science Foundation (AST-1717000). We also thank Tiago Campante for providing the best-fitting asteroseismic model for Kepler-129. M.R.K. is supported by the NSF Graduate Research Fellowship, grant No. DGE 1339067. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. Facilities: Keck(HIRES) - , Kepler. - Software: Radvel (Fulton et al. 2018), Lightkurve (Lightkurve Collaboration et al. 2018), REBOUND (Rein & Liu 2012).Attached Files
Published - Zhang_2021_AJ_162_89.pdf
Submitted - 2105.03446.pdf
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Additional details
- Eprint ID
- 110250
- Resolver ID
- CaltechAUTHORS:20210813-181202161
- Beatrice Watson Parrent Fellowship
- 80NSSC19K0597
- NASA
- Alfred P. Sloan Foundation
- AST-1717000
- NSF
- DGE-1339067
- NSF Graduate Research Fellowship
- NASA/JPL/Caltech
- Created
-
2021-08-16Created from EPrint's datestamp field
- Updated
-
2021-08-16Created from EPrint's last_modified field
- Caltech groups
- Astronomy Department, Infrared Processing and Analysis Center (IPAC)