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The SOPHIE search for northern extrasolar planets
XV. A warm Neptune around the M dwarf Gl 378

M. Hobson, X. Delfosse, N. Astudillo-Defru, I. Boisse, R. F. Díaz, F. Bouchy, X. Bonfils, T. Forveille, L. Arnold, S. Borgniet, V. Bourrier, B. Brugger, N. Cabrera Salazar, B. Courcol, S. Dalal, M. Deleuil, O. Demangeon, X. Dumusque, N. Hara, G. Hébrard, F. Kiefer, T. A. Lopez, L. Mignon, G. Montagnier, O. Mousis, C. Moutou, F. Pepe, J. Rey, A. Santerne, N. C. Santos, M. Stalport, D. Ségransan, S. Udry, P. A. Wilson

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 MEarth 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.

Keywords
techniques: radial velocities / planetary systems / stars: late-type / stars: individual: G1 378

Notes
Based on observations collected with the SOPHIE spectrograph on the 1.93 m telescope at the Observatoire de Haute-Provence (CNRS), France, by the SOPHIE Consortium.

Astronomy and Astrophysics
Volume 625, Article Number A18, Number of pages 8
2019 May

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Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia