Bibcode
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.; Alonso, R.; 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.
Bibliographical reference
Astronomy and Astrophysics, Volume 618, id.A33, 16 pp.
Advertised on:
10
2018
Journal
Citations
39
Refereed citations
35
Description
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.
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Exoplanets and Astrobiology
The search for life in the universe has been driven by recent discoveries of planets around other stars (known as exoplanets), becoming one of the most active fields in modern astrophysics. The growing number of new exoplanets discovered in recent years and the recent advance on the study of their atmospheres are not only providing new valuable
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