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 de Astrofísica 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 de Astrofísica de Canarias
D. Nespral
University of La Laguna
Instituto de Astrofísica de Canarias
G. Antoniciello
University of Turin
H. Deeg
University of La Laguna
Instituto de Astrofísica 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 de Astrofísica 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 de Astrofísica 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- A93Exoplanets from space – CHEOPS and PLATO, ESA’s next two projects
Swedish National Space Board (174/18), 2017-01-01 -- 2022-12-31.
Subject Categories
Astronomy, Astrophysics and Cosmology
Roots
Basic sciences
DOI
10.1051/0004-6361/201730885