K2-111: an old system with two planets in near-resonance

A Mortier, M R Zapatero Osorio, L Malavolta, Y Alibert, K Rice, J Lillo-Box, A Vanderburg, M Oshagh, L Buchhave, V Adibekyan, E Delgado Mena, M Lopez-Morales, D Charbonneau, S G Sousa, C Lovis, L Affer, C Allende Prieto, S C C Barros, S Benatti, A S BonomoW Boschin, F Bouchy, A Cabral, A Collier Cameron, R Cosentino, S Cristiani, O D S Demangeon, P Di Marcantonio, V D’Odorico, X Dumusque, D Ehrenreich, P Figueira, A Fiorenzano, A Ghedina, J I González Hernández, J Haldemann, A Harutyunyan, R D Haywood, D W Latham, B Lavie, G Lo Curto, J Maldonado, A Manescau, C J A P Martins, M Mayor, D Mégevand, A Mehner, G Micela, P Molaro, E Molinari, N J Nunes, F A Pepe, E Palle, D Phillips, G Piotto, M Pinamonti, E Poretti, M Riva, R Rebolo, N C Santos, D Sasselov, A Sozzetti, A Suárez Mascareño, S Udry, R G West, C A Watson, T G Wilson

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)

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.
Original languageEnglish
Pages (from-to)5004-5021
Number of pages18
JournalMonthly Notices of the Royal Astronomical Society
Volume499
Issue number4
Early online date27 Oct 2020
DOIs
Publication statusPublished - Dec 2020

Keywords

  • Techniques: photometric
  • Techniques: radial velocities
  • Techniques: spectroscopic
  • Planets and satellites: detection
  • Stars: individual (K2-111)

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