K2-111 : an old system with two planets in near-resonance
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+0.11−0.091.82−0.09+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.
Citation
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
Publication
Monthly Notices of the Royal Astronomical Society
Status
Peer reviewed
ISSN
0035-8711Type
Journal article
Description
ACC 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).Collections
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