| Issue |
A&A
Volume 711, July 2026
|
|
|---|---|---|
| Article Number | A229 | |
| Number of page(s) | 10 | |
| Section | Planets, planetary systems, and small bodies | |
| DOI | https://doi.org/10.1051/0004-6361/202660788 | |
| Published online | 17 July 2026 | |
Dynamical analysis of the 5:1 mean-motion resonance of the HD202206 system
1
Department of Earth and Planetary Sciences, The University of Hong Kong,
Pokfulam Road,
Hong Kong
2
Department of Physics, The University of Hong Kong,
Pokfulam Road,
Hong Kong
3
Hong Kong Institute for Astronomy and Astrophysics,
Hong Kong
4
Landessternwarte, Zentrum für Astronomie der Universität Heidelberg,
Königstuhl 12,
69117
Heidelberg,
Germany
5
Department of Astronomy, Faculty of Physics, Sofia University “St Kliment Ohridski”,
5 James Bourchier Blvd,
1164
Sofia,
Bulgaria
6
Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences,
Tsarigradsko Shose 72,
1784
Sofia,
Bulgaria
★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.
Received:
5
May
2026
Accepted:
23
June
2026
Abstract
Context. The HD 202206 system, which features two substellar companions with a 5:1 period ratio around a solar-type star, offers a rare opportunity to study high-order mean-motion resonances and provides new insights into the formation and evolution of substellar companions in extrasolar planetary systems.
Aims. We revisited the HD 202206 system, aiming to conduct a more comprehensive analysis of orbital inclinations, companion masses, resonance dynamics, and potential formation mechanisms.
Methods. Our analysis of the astrometric jitter around the best fit in the Gaia DR3 catalog and the proper motion anomalies between HIPPARCOS and Gaia places robust constraints on the orbital inclinations. We performed a new dynamical fit to all available radial velocity data from the CORALIE and HARPS spectrographs. We assessed the dynamical configuration and long-term stability of the system using samples generated by nested sampling.
Results. Our analysis shows that the orbital inclinations are strongly constrained to about 51°. Consequently, the best-fit dynamical solution, assuming a coplanar and inclined (i = 51°) configuration, yields an inner brown dwarf of 21.56 MJ and an outer giant planet of 3.12 MJ. The corresponding orbital periods are 256.26 days and 1298.87 days, with eccentricities of 0.426 and 0.180. An investigation of the five relevant resonance angles shows that only one is librating with a large amplitude. Our stability analysis confirms that the system is dynamically stable.
Conclusions. Our results provide new constraints on the masses and inclination of the system, challenging earlier claims of a face-on configuration and shedding light on the formation and evolution of substellar companions in extrasolar planetary systems.
Key words: methods: data analysis / methods: numerical / techniques: radial velocities / planets and satellites: dynamical evolution and stability
© The Authors 2026
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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