A planetary system with a sub-Neptune planet in the habitable zone of TOI-2093

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Aims . We aim to confirm and measure the mass of the transiting planet candidate around the K5 V star TOI-2093, previously announced by the Transiting Exoplanet Survey Satellite (TESS) project. Methods . We combined photometric data from 32 sectors between 2019 and 2024 with 86 radial velocity measurements obtained with the CARMENES spectrograph over a period of 2.4 years, along with a series of ground-based, broadband photometric monitoring campaigns to characterize the host star and the transiting planet candidate, as well as to search for additional planets in the system. Our data indicate that TOI-2093 is a main-sequence star located at a distance of 83 pc, with solar metallicity, and a rotation period of 43.8±1.8 d. Results . We have confirmed the planetary nature of the TESS transiting planet candidate, named TOI-2093 c, through the detection of its Keplerian signal in the spectroscopic data. We measured a planetary radius of 2.30±0.12 R ⊕ , a Neptune-like mass of 15.8 −3.8 +3.6 M ⊕ , and an orbital period of 53.81149±0.00017 d. This makes TOI-2093 c the smallest exoplanet known in the habitable zone of a main-sequence FGK star. Given its size and relatively high density, TOI-2093 c belongs to a class of planets with no analog in the Solar System. In addition, the CARMENES data revealed the presence of a second planet candidate with a minimum mass of 10.6±2.5 M ⊕ and an orbital period of 12.836±0.021 d. This inner planet, which we designated TOI-2093 b, shows no detectable photometric transit in the TESS light curves. The orbital planes of the two planets are misaligned by more than 1.6° despite the near 4:1 mean-motion resonance of their orbital periods.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.