K2-106, a system containing a metal-rich planet and a planet of lower density
Journal article, 2017

Planets in the mass range from 2 to 15 M_Earth 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.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. Although the two planets have similar masses, their densities are very different. For K2-106b we derive Mb=8.36-0.94+0.96 M_Earh, Rb=1.52+/-0.16 R_Earth, and a high density of 13.1-3.6+5.4 g/cm^3. For K2-106c, we find Mc=5.8-3.0+3.3 M_Earth, Rc=2.50-0.26+0.27 R_Earth and a relatively low density of 2.0-1.1+1.6 g/cm^3.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.

techniques: radial velocities

techniques: photometric

planetary systems

stars: abundances

stars: individual: TYC 608-458-1

Author

E. W. Guenther

Thüringer Landessternwarte Tautenburg

Instituto Astrofisico de Canarias

O. Barragán

University of Turin

F. Dai

Massachusetts Institute of Technology (MIT)

D. Gandolfi

University of Turin

T. Hirano

Tokyo Institute of Technology

Malcolm Fridlund

Astronomy and Plasmaphysics

L. Fossati

Institut fur Weltraumforschung

A. Chau

University of Zürich

R. Helled

University of Zürich

J. Korth

University of Cologne

J. Prieto-Arranz

University of La Laguna

Instituto Astrofisico de Canarias

D. Nespral

University of La Laguna

Instituto Astrofisico de Canarias

G. Antoniciello

University of Turin

H. Deeg

University of La Laguna

Instituto Astrofisico de Canarias

M. Hjorth

Aarhus University

S. Grziwa

University of Cologne

S. Albrecht

Aarhus University

A. Hatzes

Thüringer Landessternwarte Tautenburg

H. Rauer

German Aerospace Center (DLR)

Technische Universität Berlin

Sz. Csizmadia

German Aerospace Center (DLR)

A. M. S. Smith

German Aerospace Center (DLR)

J. Cabrera

German Aerospace Center (DLR)

N. Narita

National Institutes of Natural Sciences

University of Tokyo

National Astronomical Observatory of Japan

P. Arriagada

Carnegie Institution of Washington

J. Burt

Massachusetts Institute of Technology (MIT)

R. P. Butler

Carnegie Institution of Washington

W. D. Cochran

The University of Texas at Austin

J. D. Crane

Carnegie Observatories

Ph. Eigmüller

German Aerospace Center (DLR)

A. Erikson

German Aerospace Center (DLR)

J. A. Johnson

Harvard-Smithsonian Center for Astrophysics

A. Kiilerich

Aarhus University

D. Kubyshkina

Institut fur Weltraumforschung

E. Palle

Instituto Astrofisico de Canarias

University of La Laguna

Carina Persson

Astronomy and Plasmaphysics

M. Patzold

University of Cologne

S. Sabotta

Thüringer Landessternwarte Tautenburg

B. Sato

Tokyo Institute of Technology

St. A. Shectman

Carnegie Observatories

J. K. Teske

Carnegie Observatories

Carnegie Institution of Washington

I. B. Thompson

Carnegie Observatories

V. Van Eylen

Leiden University

G. Nowak

Instituto Astrofisico de Canarias

University of La Laguna

A. Vanderburg

Harvard-Smithsonian Center for Astrophysics

J. N. Winn

Princeton University

R. A. Wittenmyer

University of Southern Queensland

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 608 93- A93

Exoplanets from space – CHEOPS and PLATO, ESA’s next two projects

Swedish National Space Board, 2017-01-01 -- 2022-12-31.

Subject Categories

Astronomy, Astrophysics and Cosmology

Roots

Basic sciences

DOI

10.1051/0004-6361/201730885

More information

Latest update

9/10/2019