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

dc.contributor.authorMontes Gutiérrez, David
dc.contributor.authorotros, ...
dc.description© 2018. The American Astronomical Society. All rights reserved. Artículo firmado por 25 autores. CARMENES is an instrument for the Centro Astronómico Hispano-Alemán de Calar Alto (CAHA, Almeria, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Científicas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max-Planck-Institut fur Astronomie, Instituto de Astrofísica de Andalucía, Landessternwarte Konigstuhl, Institut de Ciencies de l'Espai, Insitut fur Astrophysik Gottingen, Universidad Complutense de Madrid, Thuringer Landessternwarte Tautenburg, Instituto de Astrofísica de Canarias, Hamburger Sternwarte, Centro de Astrobiología, and Centro Astronómico Hispano-Alemán), with additional contributions by the Spanish Ministry of Economy, the German Science Foundation (DFG), the states of Baden-Wurttemberg and Niedersachsen, and the Junta de Andalucía. P.S. would like to thank Christoph Mordasini for his helpful comments on an early draft and Sudeshna Boro-Saikia for her help on calculating the calcium indices of the HARPS data set. 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). We thank the anonymous referee for useful comments that improved the paper.
dc.description.abstractK2-18 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 similar to 2 R-circle plus and an orbital period of similar to 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 similar to 3.5 m s(-1). and a mass of M-b similar to 9 M-circle plus, yielding a bulk density around rho(b) similar to 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.
dc.description.departmentDepto. de Física de la Tierra y Astrofísica
dc.description.facultyFac. de Ciencias Físicas
dc.description.sponsorshipMinisterio de Economía y Competitividad (MINECO)
dc.description.sponsorshipMinisterio de Economía y Competitividad (MINECO)/FEDER
dc.description.sponsorshipGerman Max-Planck-Gesellschaft (MPG)
dc.description.sponsorshipSpanish Consejo Superior de Investigaciones Cientificas (CSIC)
dc.description.sponsorshipEuropean Union through FEDER/ERF
dc.description.sponsorshipMax-Planck-Institut fur Astronomie
dc.description.sponsorshipInstituto de Astrofísica de Andalucía
dc.description.sponsorshipLandessternwarte Konigstuhl
dc.description.sponsorshipInstitut de Ciencies de l'Espai
dc.description.sponsorshipInsitut fur Astrophysik Gottingen
dc.description.sponsorshipUniversidad Complutense de Madrid
dc.description.sponsorshipThuringer Landessternwarte Tautenburg
dc.description.sponsorshipInstituto de Astrofísica de Canarias
dc.description.sponsorshipHamburger Sternwarte
dc.description.sponsorshipCentro de Astrobiología
dc.description.sponsorshipCentro Astronómico Hispano-Alemán
dc.description.sponsorshipSpanish Ministry of Economy; German Science Foundation (DFG)
dc.description.sponsorshipStates of Baden-Wurttemberg and Niedersachsen
dc.description.sponsorshipJunta de Andalucía
dc.description.sponsorshipGeneralitat de Catalunya/CERCA program
dc.description.sponsorshipDeutsche Forschungsgemeinschaft (DFG)
dc.journal.titleAstronomical journal
dc.publisherIOP Publishing Ltd
dc.relation.projectID(AYA2016-79425-C3-1; AYA2016-79425-C3-2; AYA2016-79425-C3-3-P; AYA2015-69350-C3-2-P)
dc.relation.projectIDHA 3279/11-1
dc.rights.accessRightsopen access
dc.subject.keywordExtrasolar planets
dc.subject.ucmAstronomía (Física)
dc.titleThe CARMENES Search for Exoplanets around M Dwarfs: A Low-mass Planet in the Temperate Zone of the Nearby K2-18
dc.typejournal article
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