K2-111 : an old system with two planets in near-resonance
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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+0.11−0.091.82−0.09+0.11 R⊕ and a mass of 5.29+0.76−0.775.29−0.77+0.76 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.
Mortier , A , Zapatero Osorio , M R , Malavolta , L , Alibert , Y , Rice , K , Lillo-Box , J , Vanderburg , A , Oshagh , M , Buchhave , L , Adibekyan , V , Delgado Mena , E , Lopez-Morales , M , Charbonneau , D , Sousa , S G , Lovis , C , Affer , L , Allende Prieto , C , Barros , S C C , Benatti , S , Bonomo , A S , Boschin , W , Bouchy , F , Cabral , A , Collier Cameron , A , Cosentino , R , Cristiani , S , Demangeon , O D S , Di Marcantonio , P , D’Odorico , V , Dumusque , X , Ehrenreich , D , Figueira , P , Fiorenzano , A , Ghedina , A , González Hernández , J I , Haldemann , J , Harutyunyan , A , Haywood , R D , Latham , D W , Lavie , B , Lo Curto , G , Maldonado , J , Manescau , A , Martins , C J A P , Mayor , M , Mégevand , D , Mehner , A , Micela , G , Molaro , P , Molinari , E , Nunes , N J , Pepe , F A , Palle , E , Phillips , D , Piotto , G , Pinamonti , M , Poretti , E , Riva , M , Rebolo , R , Santos , N C , Sasselov , D , Sozzetti , A , Suárez Mascareño , A , Udry , S , West , R G , Watson , C A & Wilson , T G 2020 , ' K2-111 : an old system with two planets in near-resonance ' , Monthly Notices of the Royal Astronomical Society , vol. 499 , no. 4 , pp. 5004-5021 . https://doi.org/10.1093/mnras/staa3144
Monthly Notices of the Royal Astronomical Society
Copyright © 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the final published version of the work, which was originally published at https://doi.org/10.1093/mnras/staa3144.
DescriptionACC acknowledges support from the Science and Technology Facilities Council (STFC) consolidated grant number ST/R000824/1. CAW would like to acknowledge support from UK STFC grant ST/P000312/1. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (project FOUR ACES; grant agreement no. 724427).
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