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

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

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

Mark

Persson, C. M. ; Fridlund, M. ; Barragán, O. ; Dai, F. ; Gandolfi, D. ; Hatzes, A. P. ; Hirano, T. ; Grziwa, S. ; Korth, J. ^LU and Prieto-Arranz, J. , et al. (2018) In Astronomy and Astrophysics 618.

Abstract: 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... (More); 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: M_p ≈ 7.4 ± 2.2 M_⊕ from the GP regression and M_p ≈ 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.
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Please use this url to cite or link to this publication: https://lup.lub.lu.se/record/73de0280-8353-4ce9-86ce-51b2e4a8b176

author

Persson, C. M. ; Fridlund, M. ; Barragán, O. ; Dai, F. ; Gandolfi, D. ; Hatzes, A. P. ; Hirano, T. ; Grziwa, S. ; Korth, J. ^LU and Prieto-Arranz, J. , et al. (More)

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

publishing date

2018-10-01

type

Contribution to journal

publication status

published

keywords

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

in

Astronomy and Astrophysics

volume

618

article number

A33

publisher

EDP Sciences

external identifiers

scopus:85055046732

ISSN

0004-6361

DOI

10.1051/0004-6361/201832867

language

English

LU publication?

no

additional info

id

73de0280-8353-4ce9-86ce-51b2e4a8b176

date added to LUP

2023-02-02 11:18:17

date last changed

2023-02-20 14:30:56

@article{73de0280-8353-4ce9-86ce-51b2e4a8b176,
  abstract     = {{<p>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<sub>⊕</sub> and radius 0.72 ± 0.03 R<sub>⊕</sub>. Planet b is found to have a radius of 1.75<sub>-0.10</sub>                             <sup>+0.17</sup> R<sub>⊕</sub> and a 2.17-day orbit in agreement with previous results. We find consistent results for the planet mass from both models: M<sub>p</sub> ≈ 7.4 ± 2.2 M<sub>⊕</sub> from the GP regression and M<sub>p</sub> ≈ 8.0 ± 1.6 M<sub>⊕</sub> from the FCO technique, which implies that this planet is a super-Earth. The incident stellar flux is 2.48<sub>-48</sub>                             <sup>+220</sup> F<sub>⊕</sub>. 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.</p>}},
  author       = {{Persson, C. M. and Fridlund, M. and Barragán, O. and Dai, F. and Gandolfi, D. and Hatzes, A. P. and Hirano, T. and Grziwa, S. and Korth, J. and Prieto-Arranz, J. and Fossati, L. and Van Eylen, V. and Justesen, A. B. and Livingston, J. and Kubyshkina, D. and Deeg, H. J. and Guenther, E. W. and Nowak, G. and Cabrera, J. and Eigmüller, Ph and Csizmadia, Sz and Smith, A. M.S. and Erikson, A. and Albrecht, S. and Sobrino, Alonso and Cochran, W. D. and Endl, M. and Esposito, M. and Fukui, A. and Heeren, P. and Hidalgo, D. and Hjorth, M. and Kuzuhara, M. and Narita, N. and Nespral, D. and Palle, E. and Pätzold, M. and Rauer, H. and Rodler, F. and Winn, J. N.}},
  issn         = {{0004-6361}},
  keywords     = {{Planetary systems; Planets and satellites: Atmospheres; Planets and satellites: composition; Stars: individual: K2-216; Techniques: photometric; Techniques: radial velocities}},
  language     = {{eng}},
  month        = {{10}},
  publisher    = {{EDP Sciences}},
  series       = {{Astronomy and Astrophysics}},
  title        = {{Super-Earth of 8 M<sub>⊕</sub> in a 2.2-day orbit around the K5V star K2-216}},
  url          = {{http://dx.doi.org/10.1051/0004-6361/201832867}},
  doi          = {{10.1051/0004-6361/201832867}},
  volume       = {{618}},
  year         = {{2018}},
}

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