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New Dynamical State and Habitability of the HD 45364 Planetary System

Li, Zhexing and Kane, Stephen R. and Dalba, Paul A. and Howard, Andrew W. and Isaacson, Howard T. (2022) New Dynamical State and Habitability of the HD 45364 Planetary System. Astronomical Journal, 164 (4). Art. No. 163. ISSN 0004-6256. doi:10.3847/1538-3881/ac8d63.

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Planetary systems with multiple giant planets provide important opportunities to study planetary formation and evolution. The HD 45364 system hosts two giant planets that reside within the habitable zone (HZ) of their host star and was the first system discovered with a 3:2 mean motion resonance (MMR). Several competing migration theories with different predictions have previously provided explanations regarding the observed resonance through dynamical simulations that utilized limited data. Here, over ten years since the original discovery, we revisit the system with a substantially increased radial velocity (RV) sample from High Accuracy Radial Velocity Planet Searcher spectrograph and High Resolution Echelle Spectrometer that significantly extends the observational baseline. We present the revised orbital solutions for the two planets using both Keplerian and dynamical models. Our RV models suggest orbits that are more circular and separated than those previously reported. As a result, the predicted strong planet–planet interactions were not detected. The system dynamics were reanalyzed, and the planet pair was found to exhibit apsidal behavior of both libration and circulation, indicating a quasi-resonance state rather than being truly in MMR. The new orbital solution and dynamical state of the system confirm migration models that predicted near-circular orbits as the preferred scenario. We also study the habitability prospects of this system and found that an additional Earth-mass planet and exomoons in the HZ are possible. This work showcases the importance of continued RV observations and its impact on our knowledge of the system’s dynamical history. HD 45364 continues to be an interesting target for both planetary formation and habitability studies.

Item Type:Article
Related URLs:
URLURL TypeDescription
Li, Zhexing0000-0002-4860-7667
Kane, Stephen R.0000-0002-7084-0529
Dalba, Paul A.0000-0002-4297-5506
Howard, Andrew W.0000-0001-8638-0320
Isaacson, Howard T.0000-0002-0531-1073
Additional Information:The authors wish to thank Hanno Rein for discussion and suggestions regarding the use of the REBOUND package. The authors also would like to thank Rory Barnes for conversation regarding the system’s dynamics. We thank the anonymous referee for the valuable comments that greatly improve the presentation of this work. P.D. acknowledges support from a 51 Pegasi b Postdoctoral Fellowship from the Heising-Simons Foundation. Dynamical simulations in this paper made use of the REBOUND code, which is freely available at 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. This work has also made use of The Habitable Zone Gallery at (Kane & Gelino 2012). The results reported herein benefited from collaborations and/or information exchange within NASA’s Nexus for Exoplanet System Science (NExSS) research coordination network sponsored by NASA’s Science Mission Directorate.
Group:Astronomy Department
Funding AgencyGrant Number
Heising-Simons Foundation51 Pegasi b Fellowship
Issue or Number:4
Record Number:CaltechAUTHORS:20221010-454096500.15
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:117300
Deposited By: Research Services Depository
Deposited On:13 Oct 2022 21:34
Last Modified:13 Oct 2022 21:34

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