K2-111 b - A short period super-Earth transiting a metal poor, evolved old star
Journal article, 2017

Context. From a light curve acquired through the K2 space mission, the star K2-111(EPIC 210894022) has been identified as possibly orbited by a transiting planet. Aims: Our aim is to confirm the planetary nature of the object and derive its fundamental parameters. Methods: We analyse the light curve variations during the planetary transit using packages developed specifically for exoplanetary transits. Reconnaissance spectroscopy and radial velocity observations have been obtained using three separate telescope and spectrograph combinations. The spectroscopic synthesis package SME has been used to derive the stellar photospheric parameters that were used as input to various stellar evolutionary tracks in order to derive the parameters of the system. The planetary transit was also validated to occur on the assumed host star through adaptive imaging and statistical analysis. Results: The star is found to be located in the background of the Hyades cluster at a distance at least 4 times further away from Earth than the cluster itself. The spectrum and the space velocities of K2-111 strongly suggest it to be a member of the thick disk population. The co-added high-resolution spectra show that that it is a metal poor ([Fe/H] = - 0.53 ± 0.05 dex) and α-rich somewhat evolved solar-like star of spectral type G3. We find Teff = 5730 ± 50 K, log g⋆ = 4.15 ± 0.1 cgs, and derive a radius of R⋆ = 1.3 ± 0.1 R⊙ and a mass of M⋆ = 0.88 ± 0.02 M⊙. The currently available radial velocity data confirms a super-Earth class planet with a mass of 8.6 ± 3.9 M⊕ and a radius of 1.9 ± 0.2 R⊕. A second more massive object with a period longer than about 120 days is indicated by a long-term radial velocity drift. Conclusions: The radial velocity detection together with the imaging confirms with a high level of significance that the transit signature is caused by a planet orbiting the star K2-111. This planet is also confirmed in the radial velocity data. A second more massive object (planet, brown dwarf, or star) has been detected in the radial velocity signature. With an age of ≳10 Gyr this system is one of the oldest where planets are hitherto detected. Further studies of this planetary system are important since it contains information about the planetary formation process during a very early epoch of the history of our Galaxy.

techniques: spectroscopic

techniques: photometric

planetary systems

stars: individual: K2-111 b

Author

Malcolm Fridlund

Astronomy and Plasmaphysics

E. Gaidos

University of Hawaii

O. Barragán

University of Turin

Carina Persson

Astronomy and Plasmaphysics

D. Gandolfi

University of Turin

J. Cabrera

German Aerospace Center (DLR)

T. Hirono

Tokyo Institute of Technology

M. Kuzuhara

National Astronomical Observatory of Japan

National Institutes of Natural Sciences

Sz. Csizmadia

German Aerospace Center (DLR)

G. Nowak

Instituto Astrofisico de Canarias

University of La Laguna

M. Endl

The University of Texas at Austin

S. Grziwa

University of Cologne

J. Korth

University of Cologne

J. Pfaff

Technische Universität Berlin

B. Bitsch

Lund University

A. Johansen

Lund University

A. J. Mustill

Lund University

M. B. Davies

Lund University

H. Deeg

University of La Laguna

Instituto Astrofisico de Canarias

E. Palle

Instituto Astrofisico de Canarias

University of La Laguna

W. D. Cochran

The University of Texas at Austin

P. Eigmüller

German Aerospace Center (DLR)

A. Erikson

German Aerospace Center (DLR)

E. W. Guenther

Thüringer Landessternwarte Tautenburg

A. Hatzes

Thüringer Landessternwarte Tautenburg

A. Kiilerich

Massachusetts Institute of Technology (MIT)

Aarhus University

Princeton University

T. Kudo

National Astronomical Observatory of Japan

P. MacQueen

The University of Texas at Austin

N. Narita

University of Tokyo

National Astronomical Observatory of Japan

National Institutes of Natural Sciences

D. Nespral

Instituto Astrofisico de Canarias

University of La Laguna

M. Patzold

University of Cologne

J. Prieto-Arranz

Instituto Astrofisico de Canarias

University of La Laguna

H. Rauer

German Aerospace Center (DLR)

Technische Universität Berlin

V. Van Eylen

Heidelberg-Königstuhl State Observatory

Astronomy and Astrophysics

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

Vol. 604 A16- A16

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

10.1051/0004-6361/201730822

More information

Latest update

9/10/2019