A super-Earth orbiting the early-M dwarf GJ7^★

¹ Centro de Astrobiología, CSIC-INTA, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
² Instituto de Astrolísica de Canarias, Avda. Vía Láctea s/n, 38205 La Laguna, Tenerile, Spain
³ Dept. Astrolísica, Universidad de La Laguna, 38206 La Laguna, Tenerile, Spain
⁴ Instituto de Astrolísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal
⁵ Dept. de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Rua Campo Alegre, 4169-007 Porto, Portugal
⁶ Observatoire de l’Université de Genève, 51 chemin Pegasi, 1290 Sauverny, Switzerland
⁷ Light Bridges S.L., Avda. Alcalde Ramírez Bethencourt, 17, 35004 Las Palmas de Gran Canaria, Spain
⁸ INAF–Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese, Italy
⁹ INAF–Osservatorio Astronomico di Trieste, Via G.B. Tiepolo, 11, 34143 Trieste, Italy
¹⁰ IFPU – Institute lor Fundamental Physics ol the Universe, via Beirut 2, 34151 Trieste, Italy
¹¹ INFN–National Institute lor Nuclear Physics, via Valerio 2, 34127 Trieste, Italy
¹² Space Research and Planetary Sciences, Physics Institute, University ol Bern, Bern, Switzerland
¹³ Center lor Space and Habitability, University ol Bern, Bern, Switzerland
¹⁴ Dept. de Matemática y Física Aplicadas, Univ. Católica de la Santísima Concepción, Alonso de Rivera 2850, Concepción, Chile
¹⁵ Centro de Astrolísica do Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
¹⁶ Observatoire François-Xavier Bagnoud – OFXB, 3961 Saint-Luc, Switzerland

^★★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 8 February 2024
Accepted: 17 November 2025

Abstract

We aim to characterize the nearby (23.78 pc), low-mass planetary system GJ7 (TOI-198), which consists of an M0-type star and a terrestrial planet. Using photometric data from three sectors of the Transiting Exoplanet Survey Satellite (TESS) and a follow-up on the planetary transit observed by the Characterizing ExOPlanets Satellite (CHEOPS), along with 87 precise radial velocities obtained with the Echelle SPectrograph lor Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) spectrograph, we confidently confirm the planet and infer its properties. Planet GJ7 b has a mass of M_p = 3.17_−0.65^+0.64 M_⊕ and a radius of R_p = 1.36 ± 0.13 R_⊕. It orbits at a distance of a = 0.0675_−0.0082^+0.0067 au from its host star with an orbital period of P = 10.215213_−0.000010^+0.000011. We impose a 3σ upper limit on the planetary eccentricity of e ≤ 0.15. These parameters imply that GJ7 b has a high density, ρ_p = 6.89_−2.78^+4.27 gcm⁻³, positioning it within the region of the rocky, Earth-like planets on the mass–radius diagram and interior to the inner edge of the habitable zone around its parent star. Additionally, we find that the host star is a slow rotator and is slightly metal-depleted ([Fe/H] = −0.66 ± 0.10 dex), making GJ7 one of the lew planetary systems accurately characterized in the domain of subsolar iron abundances. TESS photometry does not show additional transit-like features attributable to planets with radii greater than ≈90% that of Earth. The high number of radial velocity measurements enables us to determine that possible transiting and non-transiting planet candidates with masses lower than hall the mass of GJ7 b would have eluded detection in our in-depth study. The stellar activity, although moderate, shows a significant radial velocity amplitude of about 4 ms⁻¹ and poses a challenge lor detecting planets with masses lower than Earth around GJ7.