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Kepler-1656b’s Extreme Eccentricity: Signature of a Gentle Giant

Angelo, Isabel and Naoz, Smadar and Petigura, Erik and MacDougall, Mason and Stephan, Alexander P. and Isaacson, Howard and Howard, Andrew W. (2022) Kepler-1656b’s Extreme Eccentricity: Signature of a Gentle Giant. Astronomical Journal, 163 (5). Art. No. 227. ISSN 0004-6256. doi:10.3847/1538-3881/ac6094.

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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 the semimajor 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꜀ = 0.40 ± 0.09 M_(jup) and P꜀ = 1919 ± 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 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Angelo, Isabel0000-0002-9751-2664
Naoz, Smadar0000-0002-9802-9279
Petigura, Erik0000-0003-0967-2893
MacDougall, Mason0000-0003-2562-9043
Stephan, Alexander P.0000-0001-8220-0548
Isaacson, Howard0000-0002-0531-1073
Howard, Andrew W.0000-0001-8638-0320
Additional Information:© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 November 30; revised 2022 February 18; accepted 2022 March 22; published 2022 April 22. I.A. is supported by the Dorothea Radcliffe Dea Fellowship and Dean's Scholarship at UCLA. We are grateful to the California Planet Search team and staff at W.M. Keck observatory for the remote observation efforts that made this study possible. I.A. would also like to thank Sanaea Rose, Judah Van Zandt, Dakotah Tyler, Jon Zink, Trevor David, and Sarah Millholland for helpful insights on the analysis and discussion sections of this paper. I.A. and S.N. acknowledge partial support from the NSF through grant No. AST-1739160. S.N. thanks Howard and Astrid Preston for their generous support. Software: Numpy (van der Walt et al. 2011), Radvel (Fulton et al. 2018), RVSearch (Rosenthal et al. 2021), corner (Foreman-Mackey 2016), astropy (Astropy Collaboration et al. 2013, 2018).
Group:Astronomy Department
Funding AgencyGrant Number
Howard and Astrid PrestonUNSPECIFIED
Subject Keywords:Exoplanet astronomy; Exoplanet dynamics; Extrasolar gaseous giant planets; Exoplanet detection methods; Exoplanet evolution; Exoplanet migration
Issue or Number:5
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet astronomy (486); Exoplanet dynamics (490); Extrasolar gaseous giant planets (509); Exoplanet detection methods (489); Exoplanet evolution (491); Exoplanet migration (2205)
Record Number:CaltechAUTHORS:20220525-90077000
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Official Citation:Isabel Angelo et al 2022 AJ 163 227
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114910
Deposited By: George Porter
Deposited On:31 May 2022 14:34
Last Modified:31 May 2022 14:34

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