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Anders Zinck Justesen

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

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  • C. M. Persson, Chalmers Univ Technol, Chalmers University of Technology, Onsala Space Observ, Dept Space Earth & Environm
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  • M. Fridlund, Leiden Univ, Leiden University, Leiden Observ
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  • O. Barragan, Univ Torino, University of Turin, Dipartimento Fis
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  • F. Dai, Princeton Univ, Princeton University, Dept Astrophys Sci
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  • D. Gandolfi, Univ Torino, University of Turin, Dipartimento Fis
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  • A. P. Hatzes, Thüringer Landessternwarte Tautenburg
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  • T. Hirano, Tokyo Inst Technol, Tokyo Institute of Technology, Dept Earth & Planetary Sci, Meguro Ku
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  • S. Grziwa, University of Cologne
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  • J. Korth, University of Cologne
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  • J. Prieto-Arranz, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • L. Fossati, Austrian Acad Sci, Austrian Academy of Sciences, Space Res Inst
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  • V. Van Eylen, Leiden Univ, Leiden University, Leiden Observ
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  • A. B. Justesen
  • J. Livingston, Univ Tokyo, University of Tokyo, Sch Sci, Dept Astron, Bunkyo Ku
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  • D. Kubyshkina, Austrian Acad Sci, Austrian Academy of Sciences, Space Res Inst
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  • H. J. Deeg, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • E. W. Guenther, Thüringer Landessternwarte Tautenburg
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  • G. Nowak, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • J. Cabrera, German Aerosp Ctr, German Aerospace Centre (DLR), Helmholtz Association, Inst Planetary Res
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  • Ph Eigmueller, German Aerosp Ctr, German Aerospace Centre (DLR), Helmholtz Association, Inst Planetary Res
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  • Sz Csizmadia, German Aerosp Ctr, German Aerospace Centre (DLR), Helmholtz Association, Inst Planetary Res
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  • A. M. S. Smith, German Aerosp Ctr, German Aerospace Centre (DLR), Helmholtz Association, Inst Planetary Res
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  • A. Erikson, German Aerosp Ctr, German Aerospace Centre (DLR), Helmholtz Association, Inst Planetary Res
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  • S. Albrecht
  • R. Alonso Sobrino, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • W. D. Cochran, Univ Texas Austin, University of Texas System, University of Texas Austin, McDonald Observ
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  • M. Endl, Univ Texas Austin, University of Texas System, University of Texas Austin, McDonald Observ
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  • M. Esposito, Thüringer Landessternwarte Tautenburg
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  • A. Fukui, Natl Astron Observ Japan, National Astronomical Observatory of Japan, National Institutes of Natural Sciences (NINS) - Japan, Okayama Astrophys Observ
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  • P. Heeren, Heidelberg Univ, Ruprecht Karls University Heidelberg, Zentrum Astron, Landessternwarte Konigstuhl
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  • D. Hidalgo, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • M. Hjorth
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  • M. Kuzuhara, Natl Inst Nat Sci, National Institutes of Natural Sciences (NINS) - Japan, Astrobiol Ctr
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  • N. Narita, Natl Inst Nat Sci, National Institutes of Natural Sciences (NINS) - Japan, Astrobiol Ctr
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  • D. Nespral, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • E. Palle, Univ La Laguna, Universidad de la Laguna, Dept Astrofis
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  • M. Paetzold, University of Cologne
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  • H. Rauer, TU Berlin, Technical University of Berlin, Ctr Astron & Astrophys
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  • F. Rodler, European So Observ, European Southern Observatory
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  • J. N. Winn, Princeton Univ, Princeton University, Dept Astrophys Sci

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 K2-216b, 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 pyanet i 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-circle dot and radius 0.72 +/- 0.03 R-circle dot. Planet b is found to have a radius of 1.75(-0.10)(+0.17) R-circle plus and a 2.17-day orbit in agreement with previous results. We find consistent results for the planet mass from both models: M-p approximate to 7.4 +/- 2.2 M-circle plus from the GP regression and M-p approximate to 8.0 +/- 1.6 M-circle plus from the FCO technique, which implies that this planet is a super-Earth. The incident stellar flux is 248(-48)(+220) F-circle plus.

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.

OriginalsprogEngelsk
Artikelnummer33
TidsskriftAstronomy & Astrophysics
Vol/bind618
Antal sider16
ISSN1432-0746
DOI
StatusUdgivet - 10 okt. 2018

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