The CARMENES search for exoplanets around M dwarfs HD147379 b: A nearby Neptune in the temperate zone of an early-M dwarf

A. Reiners, I. Ribas, M. Zechmeister, J.A. Caballero, T. Trifonov, S. Dreizler, J.C. Morales, L. Tal-Or, M. Lafarga, A. Quirrenbach, P.J. Amado, A. Kaminski, S.V. Jeffers, J. Aceituno, V.J.S. Béjar, J. Guàrdia, E.W. Guenther, H.-J. Hagen, D. Montes, V.M. Passegger, W. Seifert, A. Schweitzer, M. Cortés-Contreras, M. Abril, F.J. Alonso-Floriano, M. Ammler-von Eiff, R. Antona, G. Anglada-Escudé, H. Anwand-Heerwart, B. Arroyo-Torres, M. Azzaro, D. Baroch, D. Barrado, F.F. Bauer, S. Becerril, D. Benítez, Z.M. Berdiñas, G. Bergond, M. Blümcke, M. Brinkmöller, C. del Burgo, J. Cano, M.C. Cárdenas Vázquez, E. Casal, C. Cifuentes, A. Claret, J. Colomé, S. Czesla, E. Díez-Alonso, C. Feiz, M. Fernández, I.M. Ferro, B. Fuhrmeister, D. Galadí-Enríquez, A. Garcia-Piquer, M.L. García Vargas, L. Gesa, V. Gómez Galera, J.I. González Hernández, R. González-Peinado, U. Grözinger, S. Grohnert, A. Guijarro, E. de Guindos, J. Gutiérrez-Soto, A.P. Hatzes, P.H. Hauschildt, R.P. Hedrosa, J. Helmling, Th. Henning, I. Hermelo, R. Hernández Arabí, L. Hernández Castaño, F. Hernández Hernando, E. Herrero, A. Huber, P. Huke, E.N. Johnson, E. de Juan, M. Kim, R. Klein, J. Klüter, A. Klutsch, M. Kürster, F. Labarga, A. Lamert, M. Lampón, L.M. Lara, W. Laun, U. Lemke, R. Lenzen, R. Launhardt, M. López del Fresno, M.J. López-González, M. López-Puertas, J.F. López Salas, J. López-Santiago, R. Luque, H. Magán Madinabeitia, U. Mall et al. (72 autores adicionales no acopiados). 2018. The CARMENES search for exoplanets around M dwarfs HD147379 b: A nearby Neptune in the temperate zone of an early-M dwarf. Astronomy and Astrophysics 609, DOI: 10.1051/0004-6361/201732165

We report on the first star discovered to host a planet detected by radial velocity (RV) observations obtained within the CARMENES survey for exoplanets around M dwarfs. HD 147379 (V = 8.9 mag, M = 0.58 +/- 0.08 M-circle dot), a bright M0.0 V star at a distance of 10.7 pc, is found to undergo periodic RV variations with a semi-amplitude of K = 5.1 +/- 0.4 m s(-1) and a period of P = 86.54 +/- 0.06 d. The RV signal is found in our CARMENES data, which were taken between 2016 and 2017, and is supported by HIRES/Keck observations that were obtained since 2000. The RV variations are interpreted as resulting from a planet of minimum mass m(P) sin i = 25 +/- 2 M-circle plus, 1.5 times the mass of Neptune, with an orbital semi-major axis a = 0.32 au and low eccentricity (e < 0.13). HD 147379 b is orbiting inside the temperate zone around the star, where water could exist in liquid form. The RV time-series and various spectroscopic indicators show additional hints of variations at an approximate period of 21.1 d (and its first harmonic), which we attribute to the rotation period of the star.

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