@article{def4df3b884848fba5d5ac0f6d2765c4,
title = "K2-106, a system containing a metal-rich planet and a planet of lower density",
abstract = "Aims. Planets in the mass range from 2 to 15 M⊙ are very diverse. Some of them have low densities, while others are very dense. By measuring the masses and radii, the mean densities, structure, and composition of the planets are constrained. These parameters also give us important information about their formation and evolution, and about possible processes for atmospheric loss. Methods. We determined the masses, radii, and mean densities for the two transiting planets orbiting K2-106. The inner planet has an ultra-short period of 0.57 days. The period of the outer planet is 13.3 days. Results. Although the two planets have similar masses, their densities are very different. For K2-106b we derive Mb = 8.36+0.96-0.94 M⊙, Rb = 1.52 ± 0.16 R⊙, and a high density of 13.1+5.4-3.6 g cm-3. For K2-106c, we find Mc = 5.8+3.3-3.0 M⊙, Rc = 2.50+0.27 0:26 R⊙ and a relatively low density of 2.0+1.6-1.1 g cm-3. Conclusions. Since the system contains two planets of almost the same mass, but different distances from the host star, it is an excellent laboratory to study atmospheric escape. In agreement with the theory of atmospheric-loss processes, it is likely that the outer planet has a hydrogen-dominated atmosphere. The mass and radius of the inner planet is in agreement with theoretical models predicting an iron core containing 80+20 30% of its mass. Such a high metal content is surprising, particularly given that the star has an ordinary (solar) metal abundance. We discuss various possible formation scenarios for this unusual planet.",
keywords = "Planetary systems, Stars: Abundances, Stars: individual: TYC 608-458-1, Techniques: Radial velocities, Techniques: photometric",
author = "Guenther, {E. W.} and O. Barrag{\'a}n and F. Dai and D. Gandolfi and T. Hirano and M. Fridlund and L. Fossati and A. Chau and R. Helled and J. Korth and J. Prieto-Arranz and D. Nespral and G. Antoniciello and H. Deeg and M. Hjorth and S. Grziwa and S. Albrecht and Hatzes, {A. P.} and H. Rauer and Sz Csizmadia and Smith, {A. M.S.} and J. Cabrera and N. Narita and P. Arriagada and J. Burt and Butler, {R. P.} and Cochran, {W. D.} and Crane, {J. D.} and Ph Eigm{\"u}ller and A. Erikson and Johnson, {J. A.} and A. Kiilerich and D. Kubyshkina and E. Palle and Persson, {C. M.} and M. P{\"a}tzold and S. Sabotta and B. Sato and A. Shectman and Teske, {J. K.} and Thompson, {I. B.} and {Van Eylen}, V. and G. Nowak and A. Vanderburg and Winn, {J. N.} and Wittenmyer, {R. A.}",
note = "Funding Information: Acknowledgements. This work was generously supported by the Th{\"u}ringer Ministerium f{\"u}r Wirtschaft, Wissenschaft und Digitale Gesellschaft and the Deutsche Forschungsgemeinschaft (DFG) under the project GU 464/20-1. H.D. acknowledges support by grant ESP2015-65712-C5-4-R of the Spanish Secretary of State for R&D&i (MINECO). L.F. and D.K. acknowledge the Austrian Forschungs-f{\"o}rderungsgesellschaft FFG project “TAPAS4CHEOPS” P853993. M.F. and C.M.P. acknowledge generous support from the Swedish National Space Board. This work was supported by Japan Society for Promotion of Science (JSPS) KAKENHI Grant Number JP16K17660, and by the Astrobiology Center Project of National Institutes of Natural Sciences (NINS) (Grant Number JY280092). Results based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. Partly based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 098.C-0860(A). Australian access to the Magellan Telescopes was supported through the National Collaborative Research Infrastructure Strategy of the Australian Federal Government. Also based in part on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundaci{\'o}n Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observato-rio del Roque de los Muchachos of the Instituto de Astrof{\'i}sica de Canarias (IAC). Also partly based on observations made with the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrof{\'i}sica de Canarias. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www. cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This research has made use of the SIM-BAD database, operated at CDS, Strasbourg, France. We are grateful to Jorge Melendez, Fran{\c c}ois Bouchy, and Xavier Bonfils, who kindly agreed to exchange HARPS time with us. We thank the NOT staff members for their valuable support during the observations. D.G. gratefully acknowledges the financial support of the Programma Giovani Ricercatori – Rita Levi Montalcini – Rientro dei Cervelli (2012) awarded by the Italian Ministry of Education, Universities and Research (MIUR). Publisher Copyright: {\textcopyright} ESO 2017.",
year = "2017",
month = dec,
day = "1",
doi = "10.1051/0004-6361/201730885",
language = "English (US)",
volume = "608",
journal = "Astronomy and Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",
}