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Kepler-1656b's Extreme Eccentricity: Signature of a Gentle Giant
- Publication Year :
- 2022
-
Abstract
- Highly eccentric orbits are one of the major surprises of exoplanets relative to the Solar System and indicate rich and tumultuous dynamical histories. One system of particular interest is Kepler-1656, which hosts a sub-Jovian planet with an eccentricity of 0.8. Sufficiently eccentric orbits will shrink in semi-major axis due to tidal dissipation of orbital energy during periastron passage. Here our goal was to assess whether Kepler-1656b is currently undergoing such high-eccentricity migration, and to further understand the system's origins and architecture. We confirm a second planet in the system with $M_{\rm c}= 0.40 \pm 0.09M_{\rm jup}$ and P$_{\rm c}= 1919\pm 27\,$days. We simulated the dynamical evolution of planet b in the presence of planet c and find a variety of possible outcomes for the system, such as tidal migration and engulfment. The system is consistent with an in situ dynamical origin of planet b followed by subsequent Eccentric Kozai Lidov (EKL) perturbations that excite Kepler-1656b's eccentricity gently, i.e. without initiating tidal migration. Thus, despite its high eccentricity, we find no evidence that planet b is or has migrated through the high-eccentricity channel. Finally, we predict the outer orbit to be mutually inclined in a nearly perpendicular configuration with respect to the inner planet orbit based on the outcomes of our simulations, and make observable predictions for the inner planet's spin-orbit angle. Our methodology can be applied to other eccentric or tidally locked planets to constrain their origins, orbital configurations and properties of a potential companion.<br />Comment: Submitted to AJ;22 pages, 14 figures
- Subjects :
- Astrophysics - Earth and Planetary Astrophysics
Subjects
Details
- Database :
- arXiv
- Publication Type :
- Report
- Accession number :
- edsarx.2204.00019
- Document Type :
- Working Paper
- Full Text :
- https://doi.org/10.3847/1538-3881/ac6094