Bibcode
Fridlund, M.; Gaidos, Eric; Barragán, Oscar; Persson, Carina M.; Gandolfi, Davide; Cabrera, Juan; Hirano, Teruyuki; Kuzuhara, Masayuki; Csizmadia, Sz.; Nowak, G.; Endl, Michael; Grziwa, Sascha; Korth, Judith; Pfaff, Jeremias; Bitsch, Bertram; Johansen, Anders; Mustill, Alexander J.; Davies, Melvyn B.; Deeg, H. J.; Palle, E.; Cochran, William D.; Eigmüller, Philipp; Erikson, Anders; Guenther, Eike; Hatzes, Artie P.; Kiilerich, Amanda; Kudo, Tomoyuki; MacQueen, Phillip; Narita, Norio; Nespral, D.; Pätzold, Martin; Prieto-Arranz, J.; Rauer, Heike; Van Eylen, Vincent
Referencia bibliográfica
Astronomy and Astrophysics, Volume 604, id.A16, 13 pp.
Fecha de publicación:
7
2017
Revista
Número de citas
40
Número de citas referidas
39
Descripción
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.
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