. I.R. and J.C.M. acknowledge support
by the Spanish Ministry of Economy and Competitiveness
(MINECO) and the Fondo Europeo de Desarrollo Regional
(FEDER) through grant ESP2016-80435-C2-1-R, as well as
the support of the Generalitat de Catalunya/CERCA program.
A.P.H. acknowledges the support of the Deutsche Forschungsgemeinschaft
(DFG) grant HA 3279/11-1. J.A.C.,
P.J.A. and D.M. acknowledge support by the Spanish
Ministry of Economy and Competitiveness (MINECO) from
projects AYA2016-79425-C3-1, 2, 3-P. V.J.S.B. is supported
by program AYA2015-69350-C3-2-P from Spanish Ministry
of Economy and Competitiveness (MINECO

Aceituno, J

Amado, PJ

Anglada-Escude, G

Bejar, VJS

Caballero, JA

Dreizler, S

Hagen, H-J

Hatzes, AP

Henning, T

Jeffers, S

Kaminski, A

Kuerster, M

Lafarga, M

Launhardt, R

Mallonn, M

Marvin, C

Montes, D

Morales, JC

Quirrenbach, A

Reiners, A

Ribas, I

Sarkis, P

Tal-Or, L

Trifonov, T

Zechmeister, M

The Astronomical Journal

arXiv

K2-18 is a nearby M2.5 dwarf, located at 34 pc and hosting a transiting planet that was first discovered by the K2 mission and later confirmed with Spitzer Space Telescope observations. With a radius of ̃2 R ⊕ and an orbital period of ̃33 days, the planet lies in the temperate zone of its host star and receives stellar irradiation similar to that of Earth. Here we perform radial velocity follow-up observations with the visual channel of CARMENES with the goal of determining the mass and density of the planet. We measure a planetary semi-amplitude of K  b  ̃ 3.5 {{m}} {{{s}}}-1 and a mass of M  b  ̃ 9 M ⊕, yielding a bulk density around {ρ }b̃ 4 {{g}} {cm}}-3. This indicates a low-mass planet with a composition consistent with a solid core and a volatile- rich envelope. A signal at 9 days was recently reported using radial velocity measurements taken with the HARPS spectrograph. This was interpreted as being due to a second planet. We see a weaker, time- and wavelength-dependent signal in the CARMENES data set and thus favor stellar activity for its origin. K2-18 b joins the growing group of low- mass planets detected in the temperate zone of M dwarfs. The brightness of the host star in the near-infrared makes the system a good target for detailed atmospheric studies with the James Webb Space Telescope

Sarkis, P.

Henning, T.

Kürster, M.

Trifonov, T.

Zechmeister, M.

Tal-Or, L.

Anglada-Escudé, G.

Hatzes, A.

Lafarga, M.

Dreizler, S.

Ribas, I.

Caballero, J.

Reiners, A.

Mallonn, M.

Morales, J.

Kaminski, A.

Aceituno, J.

Amado, P.

Béjar, V.

Hagen, H.

Jeffers, S.

Quirrenbach, A.

Launhardt, R.

Marvin, C.

Montes, D.

MPG.PuRe

The CARMENES Search for Exoplanets around M Dwarfs: A Low-mass Planet in the Temperate Zone of the Nearby K2-18

The CARMENES Search for Exoplanets around M Dwarfs: A Low-mass Planet in the Temperate Zone of the Nearby K2-18

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