The SOPHIE search for northern extrasolar planets

XV. A warm Neptune around the M dwarf Gl 378^★

¹ CNRS, CNES, LAM, Aix-Marseille Université, Marseille, France
e-mail: melissa.hobson@lam.fr
² CNRS, IPAG, Université Grenoble Alpes, 38000 Grenoble, France
³ Departamento de Astronomía, Universidad de Concepción, Casilla 160-C, Concepción, Chile
⁴ Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
⁵ Instituto de Astronomía y Física del Espacio (IAFE), CONICET – Universidad de Buenos Aires, Buenos Aires, Argentina
⁶ Observatoire Astronomique de l’Université de Genève, 51 Chemin des Maillettes, 1290 Versoix, Switzerland
⁷ Observatoire de Haute-Provence, CNRS, Aix-Marseille Université, Institut Pythéas UMS 3470, 04870 Saint-Michel-l’Observatoire, France
⁸ Institut d’Astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie, 98bis boulevard Arago, 75014 Paris, France
⁹ Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal
¹⁰ Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
¹¹ ASD/IMCCE, CNRS-UMR8028, Observatoire de Paris, PSL, UPMC, 77 Avenue Denfert-Rochereau, 75014 Paris, France
¹² Canada-France-Hawaii Telescope Corporation, 65-1238 Mamalahoa Hwy, Kamuela, HI 96743, USA
¹³ Department of Physics, University of Warwick, Coventry CV4 7AL, UK
¹⁴ Centre for Exoplanets and Habitability, University of Warwick, Coventry CV4 7AL, UK

Received: 15 December 2018
Accepted: 12 February 2019

Abstract

We present the detection of a warm Neptune orbiting the M dwarf Gl 378, using radial velocity measurements obtained with the SOPHIE spectrograph at the Observatoire de Haute-Provence. The star was observed in the context of the SOPHIE exoplanet consortium’s sub-programme dedicated to finding planets around M dwarfs. Gl 378 is an M1 star, of solar metallicity, at a distance of 14.96 pc. The single planet detected, Gl 378 b, has a minimum mass of 13.02 M_Earth and an orbital period of 3.82 days, which place it at the lower boundary of the hot Neptune desert. As one of only a few such planets around M dwarfs, Gl 378 b provides important clues to the evolutionary history of these close-in planets. In particular, the eccentricity of 0.1 may point to a high-eccentricity migration. The planet may also have lost part of its envelope due to irradiation.