K2-111 b - A short period super-Earth transiting a metal poor, evolved old star
Artikel i vetenskaplig tidskrift, 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: photometric

stars: individual: K2-111 b

planetary systems

techniques: spectroscopic

Författare

Malcolm Fridlund

Astronomi och plasmafysik

E. Gaidos

University of Hawaii at Manoa

O. Barragán

Universita degli Studi di Torino

Carina Persson

Astronomi och plasmafysik

D. Gandolfi

Universita degli Studi di Torino

J. Cabrera

Deutsches Zentrum fur Luft- Und Raumfahrt

T. Hirono

Tokyo Institute of Technology

M. Kuzuhara

National Institutes of Natural Sciences

National Institutes of Natural Sciences - National Astronomical Observatory of Japan

Sz. Csizmadia

Deutsches Zentrum fur Luft- Und Raumfahrt

G. Nowak

Instituto Astrofisico de Canarias

Universidad de la Laguna

M. Endl

University of Texas at Austin

S. Grziwa

Universitat zu Koln

J. Korth

Universitat zu Koln

J. Pfaff

Technische Universitat Berlin

B. Bitsch

Lunds Universitet

A. Johansen

Lunds Universitet

A. J. Mustill

Lunds Universitet

M. B. Davies

Lunds Universitet

H. Deeg

Instituto Astrofisico de Canarias

Universidad de la Laguna

E. Palle

Instituto Astrofisico de Canarias

Universidad de la Laguna

W. D. Cochran

University of Texas at Austin

P. Eigmüller

Deutsches Zentrum fur Luft- Und Raumfahrt

A. Erikson

Deutsches Zentrum fur Luft- Und Raumfahrt

E. W. Guenther

Thuringer Landessternwarte Tautenburg

A. Hatzes

Thuringer Landessternwarte Tautenburg

A. Kiilerich

Massachusetts Institute of Technology

Aarhus Universitet

Princeton University

T. Kudo

National Institutes of Natural Sciences - National Astronomical Observatory of Japan

P. MacQueen

University of Texas at Austin

N. Narita

National Institutes of Natural Sciences - National Astronomical Observatory of Japan

National Institutes of Natural Sciences

University of Tokyo

D. Nespral

Instituto Astrofisico de Canarias

Universidad de la Laguna

M. Patzold

Universitat zu Koln

J. Prieto-Arranz

Instituto Astrofisico de Canarias

Universidad de la Laguna

H. Rauer

Technische Universitat Berlin

Deutsches Zentrum fur Luft- Und Raumfahrt

V. Van Eylen

Landessternwarte Heidelberg

Astronomy and Astrophysics

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

Vol. 604 A16- A16

Ämneskategorier

Astronomi, astrofysik och kosmologi

Fundament

Grundläggande vetenskaper

DOI

10.1051/0004-6361/201730822