K2-111: an old system with two planets in near-resonance
Date Issued
2020
Author(s)
Mortier, A.
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Zapatero Osorio, M. R.
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Alibert, Y.
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Rice, K.
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Lillo-Box, J.
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Vanderburg, A.
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Oshagh, M.
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Buchhave, L.
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Adibekyan, V.
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Delgado Mena, E.
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Lopez-Morales, M.
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Charbonneau, D.
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Sousa, S. G.
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Lovis, C.
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Allende Prieto, C.
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Barros, S. C. C.
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•
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Boschin, W.
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Bouchy, F.
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Cabral, A.
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Collier Cameron, A.
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Demangeon, O. D. S.
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Dumusque, X.
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Ehrenreich, D.
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Figueira, P.
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Fiorenzano, A.
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Ghedina, A.
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González Hernández, J. I.
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Haldemann, J.
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Harutyunyan, A.
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Haywood, R. D.
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Latham, D. W.
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Lavie, B.
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Lo Curto, G.
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Manescau, A.
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Martins, C. J. A. P.
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Mayor, M.
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Mégevand, D.
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Mehner, A.
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Nunes, N. J.
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Pepe, F. A.
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Palle, E.
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Phillips, D.
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Piotto, G.
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Rebolo, R.
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Santos, N. C.
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Sasselov, D.
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Suárez Mascareño, A.
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Udry, S.
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West, R. G.
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Watson, C. A.
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Wilson, T. G.
Abstract
This paper reports on the detailed characterization of the K2-111 planetary system with K2, WASP, and ASAS-SN photometry, as well as high-resolution spectroscopic data from HARPS-N and ESPRESSO. The host, K2-111, is confirmed to be a mildly evolved (log g = 4.17), iron-poor ([Fe/H] = -0.46), but alpha-enhanced ([α/Fe]=0.27), chromospherically quiet, very old thick disc G2 star. A global fit, performed by using PyORBIT, shows that the transiting planet, K2-111 b, orbits with a period Pb = 5.3518 ± 0.0004 d and has a planet radius of $1.82^{+0.11}_{-0.09}$ R⊕ and a mass of $5.29^{+0.76}_{-0.77}$ M⊕, resulting in a bulk density slightly lower than that of the Earth. The stellar chemical composition and the planet properties are consistent with K2-111 b being a terrestrial planet with an iron core mass fraction lower than the Earth. We announce the existence of a second signal in the radial velocity data that we attribute to a non-transiting planet, K2-111 c, with an orbital period of 15.6785 ± 0.0064 d, orbiting in near-3:1 mean motion resonance with the transiting planet, and a minimum planet mass of 11.3 ± 1.1 M⊕. Both planet signals are independently detected in the HARPS-N and ESPRESSO data when fitted separately. There are potentially more planets in this resonant system, but more well-sampled data are required to confirm their presence and physical parameters.
Volume
499
Issue
4
Start page
5004
Issn Identifier
0035-8711
Ads BibCode
2020MNRAS.499.5004M
Rights
open.access
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