Extremely Inclined Orbit of S-type Planet γ Cep Ab Induced by Eccentric Kozai-Lidov Mechanism

Xiumin Huang and Jianghui Ji

Submitted on 3 September 2022


γ Cep Ab is a typical S-type planet, which occupies a nearly perpendicular planetary orbit relative to the binary. Here we use the Markov Chain Monte Carlo (MCMC) sampler to conduct full N-body fitting and derive self-consistent orbital solutions for this hierarchical system. Then we employ the Eccentric Kozai-Lidov (EKL) mechanism to explain the extremely inclined orbit of S-type planet γ Cep Ab. The EKL mechanism plays an essential role in exploring significant oscillations of the mutual inclination imut between the planet and the secondary star. We perform qualitative analysis and extensive numerical integrations to investigate the flip conditions and timescales of γ Cep Ab's orbit. When the planetary mass is 15 MJup, the planet can reach imut 113 with the critical initial conditions of imut<60 and e1<0.7. The timescale for the first orbital flip decreases with the increase of the perturbation Hamiltonian. Flipping orbits of γ Cep Ab are confirmed to have a large possibility to retain stable based on surfaces of section and the secular stability criterion. Furthermore, we extend the application of EKL to general S-type planetary systems with a1/a20.1, where the most intense excitation of imut occurs when a1/a2=0.1 and e20.8, and the variation of planetary mass mainly affect the flip possibility where e10.3.


Comment: 21 pages, 14 figures, accepted for publication in AJ

Subjects: Astrophysics - Earth and Planetary Astrophysics; Astrophysics - Solar and Stellar Astrophysics