Bibcode
Palle, E.; Nowak, G.; Luque, R.; Hidalgo, D.; Barragán, O.; Prieto-Arranz, J.; Hirano, T.; Fridlund, M.; Gandolfi, D.; Livingston, J.; Dai, F.; Morales, J. C.; Lafarga, M.; Albrecht, S.; Alonso, R.; Amado, P. J.; Caballero, J. A.; Cabrera, J.; Cochran, W. D.; Csizmadia, Sz.; Deeg, H.; Eigmüller, Ph.; Endl, M.; Erikson, A.; Fukui, A.; Guenther, E. W.; Grziwa, S.; Hatzes, A. P.; Korth, J.; Kürster, M.; Kuzuhara, M.; Montañes Rodríguez, P.; Murgas, F.; Narita, N.; Nespral, D.; Pätzold, M.; Persson, C. M.; Quirrenbach, A.; Rauer, H.; Redfield, S.; Reiners, A.; Ribas, I.; Smith, A. M. S.; Van Eylen, V.; Winn, J. N.; Zechmeister, M.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 623, id.A41, 10 pp.
Fecha de publicación:
3
2019
Revista
Número de citas
19
Número de citas referidas
17
Descripción
Context. The Kepler extended mission, also known as K2, has provided the
community with a wealth of planetary candidates that orbit stars
typically much brighter than the targets of the original mission. These
planet candidates are suitable for further spectroscopic follow-up and
precise mass determinations, leading ultimately to the construction of
empirical mass-radius diagrams. Particularly interesting is to constrain
the properties of planets that are between Earth and Neptune in size,
the most abundant type of planet orbiting Sun-like stars with periods of
less than a few years. Aims: Among many other K2 candidates, we
discovered a multi-planetary system around EPIC 246471491, referred to
henceforth as K2-285, which contains four planets, ranging in size from
twice the size of Earth to nearly the size of Neptune. We aim here at
confirming their planetary nature and characterizing the properties of
this system. Methods: We measure the mass of the planets of the
K2-285 system by means of precise radial-velocity measurements using the
CARMENES spectrograph and the HARPS-N spectrograph. Results: With
our data we are able to determine the mass of the two inner planets of
the system with a precision better than 15%, and place upper limits on
the masses of the two outer planets. Conclusions: We find that
K2-285b has a mass of Mb =
9.68-1.37+1.21 M⊕ and a radius of
Rb = 2.59-0.06+0.06
R⊕, yielding a mean density of ρb =
3.07-0.45+0.45 g cm-3, while K2-285c
has a mass of Mc = 15.68-2.13+2.28
M⊕, radius of Rc =
3.53-0.08+0.08 R⊕, and a mean
density of ρc = 1.95-0.28+0.32 g
cm-3. For K2-285d (Rd =
2.48-0.06+0.06 R⊕) and K2-285e
(Re = 1.95-0.05+0.05
R⊕), the upper limits for the masses are 6.5
M⊕ and 10.7 M⊕, respectively. The
system is thus composed of an (almost) Neptune-twin planet (in mass and
radius), two sub-Neptunes with very different densities and presumably
bulk composition, and a fourth planet in the outermost orbit that
resides right in the middle of the super-Earth/sub-Neptune radius gap.
Future comparative planetology studies of this system would provide
useful insights into planetary formation, and also a good test of
atmospheric escape and evolution theories.
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