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korth

Judith Korth

Postdoc

korth

Super-Earth of 8 M⊕ in a 2.2-day orbit around the K5V star K2-216

Author

  • C. M. Persson
  • M. Fridlund
  • O. Barragán
  • F. Dai
  • D. Gandolfi
  • A. P. Hatzes
  • T. Hirano
  • S. Grziwa
  • J. Korth
  • J. Prieto-Arranz
  • L. Fossati
  • V. Van Eylen
  • A. B. Justesen
  • J. Livingston
  • D. Kubyshkina
  • H. J. Deeg
  • E. W. Guenther
  • G. Nowak
  • J. Cabrera
  • Ph Eigmüller
  • Sz Csizmadia
  • A. M.S. Smith
  • A. Erikson
  • S. Albrecht
  • Alonso Sobrino
  • W. D. Cochran
  • M. Endl
  • M. Esposito
  • A. Fukui
  • P. Heeren
  • D. Hidalgo
  • M. Hjorth
  • M. Kuzuhara
  • N. Narita
  • D. Nespral
  • E. Palle
  • M. Pätzold
  • H. Rauer
  • F. Rodler
  • J. N. Winn
Show all

Summary, in English

Context. Although thousands of exoplanets have been discovered to date, far fewer have been fully characterised, in particular super-Earths. The KESPRINT consortium identified K2-216 as a planetary candidate host star in the K2 space mission Campaign 8 field with a transiting super-Earth. The planet has recently been validated as well. Aims. Our aim was to confirm the detection and derive the main physical characteristics of K2-216 b, including the mass. Methods. We performed a series of follow-up observations: high-resolution imaging with the FastCam camera at the TCS and the Infrared Camera and Spectrograph at Subaru, and high-resolution spectroscopy with HARPS (La Silla), HARPS-N (TNG), and FIES (NOT). The stellar spectra were analyzed with the SpecMatch-Emp and SME codes to derive the fundamental stellar properties. We analyzed the K2 light curve with the pyaneti software. The radial velocity measurements were modelled with both a Gaussian process (GP) regression and the so-called floating chunk offset (FCO) technique to simultaneously model the planetary signal and correlated noise associated with stellar activity. Results. Imaging confirms that K2-216 is a single star. Our analysis discloses that the star is a moderately active K5V star of mass 0.70 ± 0.03 M⊕ and radius 0.72 ± 0.03 R⊕. Planet b is found to have a radius of 1.75-0.10+0.17 R⊕ and a 2.17-day orbit in agreement with previous results. We find consistent results for the planet mass from both models: Mp ≈ 7.4 ± 2.2 M⊕ from the GP regression and Mp ≈ 8.0 ± 1.6 M⊕ from the FCO technique, which implies that this planet is a super-Earth. The incident stellar flux is 2.48-48+220 F⊕. Conclusions. The planet parameters put planet b in the middle of, or just below, the gap of the radius distribution of small planets. The density is consistent with a rocky composition of primarily iron and magnesium silicate. In agreement with theoretical predictions, we find that the planet is a remnant core, stripped of its atmosphere, and is one of the largest planets found that has lost its atmosphere.

Publishing year

2018-10-01

Language

English

Publication/Series

Astronomy and Astrophysics

Volume

618

Document type

Journal article

Publisher

EDP Sciences

Keywords

  • Planetary systems
  • Planets and satellites: Atmospheres
  • Planets and satellites: composition
  • Stars: individual: K2-216
  • Techniques: photometric
  • Techniques: radial velocities

Status

Published

ISBN/ISSN/Other

  • ISSN: 0004-6361