TOI-4860 b, a short-period giant planet transiting an M3.5 dwarf

¹ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
e-mail: jose-manuel.almenara-villa@univ-grenoble-alpes.fr
² Observatoire de Genève, Département d’Astronomie, Université de Genève, Chemin Pegasi 51b, 1290 Versoix, Switzerland
³ Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK
⁴ Department of Physics, University of Warwick, Coventry, UK
⁵ Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Av. Diagonal las Torres 2640, Peñalolén, Santiago, Chile
⁶ Millennium Institute for Astrophysics (MAS), Santiago, Chile
⁷ Data Observatory Foundation, Santiago, Chile
⁸ Institut d’astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie, 98bis boulevard Arago, 75014 Paris, France
⁹ Observatoire de Haute-Provence, CNRS, Université d’Aix-Marseille, 04870 Saint-Michel-l’Observatoire, France
¹⁰ Laboratório Nacional de Astrofísica, Rua Estados Unidos 154, 37504-364, Itajubá, MG, Brazil
¹¹ CFisUC, Departamento de Física, Universidade de Coimbra, 3004-516 Coimbra, Portugal
¹² IMCCE, UMR8028 CNRS, Observatoire de Paris, PSL Université, Sorbonne Univ., 77 av. Denfert-Rochereau, 75014 Paris, France
¹³ Departamento de Matemática y Física Aplicadas, Universidad Católica de la Santísima Concepción, Alonso de Rivera 2850, Concepción, Chile
¹⁴ Université de Montréal, Département de Physique & Institut Trottier de Recherche sur les Exoplanètes, Montréal, QC H3C 3J7, Canada
¹⁵ Canada-France-Hawaii Telescope (CFHT) Corporation, CNRS UAR2208, 65-1238 Mamalahoa Hwy, Kamuela, HI 96743, USA
¹⁶ Department of Astrophysical Sciences, Princeton University, NJ 08544, USA
¹⁷ Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal
¹⁸ Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Rua Campo Alegre, 4169-007 Porto, Portugal
¹⁹ Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
²⁰ NASA Exoplanet Science Institute – Caltech/IPAC, 1200 E. California Blvd, Pasadena, CA 91125, USA
²¹ Department of Physics & Astronomy, McMaster University, 1280 Main St W, Hamilton, ON L8S 4L8, Canada
²² Department of Physics, McGill University, 3600 rue University, Montréal, Québec H3A 2T8, Canada
²³ Department of Earth and Planetary Sciences, McGill University, 3450 rue University, Montréal, Québec H3A 0E8, Canada
²⁴ Univ. Federal do Rio G. do Norte, UFRN, Dep. de Física, CP 1641, 59072-970, Natal, RN, Brazil
²⁵ Université de Toulouse, CNRS, IRAP, 14 avenue Belin, 31400 Toulouse, France
²⁶ Dept. of Earth Sciences, University of Hawai’i at Mänoa, Honolulu, HI 96822, USA
²⁷ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
²⁸ Wesleyan University, Middletown, CT 06459, USA
²⁹ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
³⁰ NASA Ames Research Center, Moffett Field, CA 94035, USA
³¹ LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
³² NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA
³³ SETI Institute, 189 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
³⁴ Physics & Astrophysics Group, Dept. of Physical & Environmental Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario, M1C 1A4, Canada
³⁵ David A. Dunlap Department of Astronomy & Astrophysics, University of Toronto. 50 St. George Street, Toronto, Ontario M5S 3H4, Canada
³⁶ Department of Physics, University of Toronto, 60 St George Street, Toronto, Ontario M5S 1A7, Canada
³⁷ Instituto de Astrofísica de Canarias (IAC), 38200 La Laguna, Tenerife, Spain
³⁸ Dept. Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
³⁹ Department of Physics and Astronomy, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, KS 66045, USA
⁴⁰ Research Institute for Advanced Computer Science, Universities Space Research Association, Washington, DC 20024, USA
⁴¹ European Southern Observatory, Alonso de Córdova 3107, Vitacura, Región Metropolitana, Chile
⁴² Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 10617, Taiwan

Received: 25 May 2023
Accepted: 8 January 2024

Abstract

We report the discovery and characterisation of a giant transiting planet orbiting a nearby M3.5V dwarf (d = 80.4pc, G = 15.1 mag, K=11.2mag, R_* = 0.358 ± 0.015 R_⊙, M_* = 0.340 ± 0.009 M_⊙). Using the photometric time series from TESS sectors 10, 36, 46, and 63 and near-infrared spectrophotometry from ExTrA, we measured a planetary radius of 0.77 ± 0.03 R_J and an orbital period of 1.52 days. With high-resolution spectroscopy taken by the CFHT/SPIRou and ESO/ESPRESSO spectrographs, we refined the host star parameters ([Fe/H] = 0.27 ± 0.12) and measured the mass of the planet (0.273 ± 0.006 M_J). Based on these measurements, TOI-4860 b joins the small set of massive planets (>80 M_E) found around mid to late M dwarfs (<0.4 R_⊙), providing both an interesting challenge to planet formation theory and a favourable target for further atmospheric studies with transmission spectroscopy. We identified an additional signal in the radial velocity data that we attribute to an eccentric planet candidate (e = 0.66 ± 0.09) with an orbital period of 427 ± 7 days and a minimum mass of 1.66 ± 0.26 M_J, but additional data would be needed to confirm this.