GI 725A b: A potential super-Earth detected with SOPHIE and SPIRou in an M dwarf binary system at 3.5 pc

¹ Centre for Exoplanet Science, SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
² Aix Marseille Univ., CNRS, CNES, LAM, Marseille, France
³ Univ. de Toulouse, CNRS, IRAP, 14 av. Belin, 31400 Toulouse, France
⁴ Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
⁵ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
⁶ Institut Trottier de Recherche sur les Exoplanètes and Département de Physique, Université de Montréal, 1375 Avenue Thérèse-Lavoie-Roux, Montréal, QC H2V 0B3, Canada
⁷ Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁸ Departamento de Matemática y Física Aplicadas, Universidad Católica de la Santísima Concepción, Alonso de Rivera 2850, Concepción, Chile
⁹ Observatoire de Paris, CNRS, LERMA, Sorbonne Université, 61 avenue de l’Observatoire, 75014 Paris, France
¹⁰ International Center for Advanced Studies (ICAS) and ICIFI (CONICET), ECyT-UNSAM, Campus Miguelete, 25 de Mayo y Francia, (1650) Buenos Aires, Argentina
¹¹ Instituto de Astrof ísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal
¹² Crimean Astrophysical Observatory, 298409 Nauchny, Crimea
¹³ Institut d’Astrophysique de Paris, CNRS, UMR 7095, Sorbonne Université, 98 bis bd Arago, 75014 Paris, France
¹⁴ Observatoire de Haute-Provence, CNRS, Université d’Aix-Marseille, 04870 Saint-Michel-l’Observatoire, France
¹⁵ Laboratório Nacional de Astrofísica, Rua Estados Unidos 154, 37504-364 Itajubá, MG, Brazil
¹⁶ Laboratoire de Météorologie Dynamique, Institut Pierre Simon Laplace, CNRS, Paris, France
¹⁷ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, France

^★ Corresponding author; pcz1@st-andrews.ac.uk

Received: 24 July 2024
Accepted: 14 November 2024

Abstract

We report the discovery of a super-Earth candidate orbiting the nearby mid-M dwarf Gl 725A using the radial velocity (RV) method. The planetary signal has been independently identified using high-precision RVs from the SOPHIE and SPIRou spectrographs, in the optical and near-infrared (NIR) domains, respectively. We modelled the stellar activity signal jointly with the planet using two Gaussian processes, one for each instrument to account for the chromaticity of the stellar activity and instrumental systematics, along with a Keplerian model. The signal was significantly detected with a RV semi-amplitude of 1.67 ± 0.20 m/s. The planet Gl725A b is found to be in an orbit compatible with circular with a period of 11.2201 ± 0.0051 days. We analysed 27 sectors of TESS photometry, for which no transit event was found. We determined a minimum mass of M_p sin i = 2.78 ± 0.35 M_⊕, which places the planet in the super-Earth regime. Using mass-radius relationships, we predict the planetary radius to be between 1.2 and 2.0 R_⊕. The proximity of Gl 725A (at only 3.5 pc) makes this new exoplanet one of the closest to Earth and joins the group of S-type low-mass planets in short orbits (P < 15 days) around close M dwarfs.