K2-111: an old system with two planets in near-resonance. Issue 4 (27th October 2020)

• Record Type: Journal Article
• Authors: 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;
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 499:Issue 4(2020)
• Page Start: 5004
• Page End: 5021
• Publication Date: 2020-10-27
• Subjects: techniques: photometric -- techniques: radial velocities -- techniques: spectroscopic -- planets and satellites: detection -- stars: individual (K2-111); Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa3144
• Languages: English
• ISSNs: 0035-8711

Abstract

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.