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We present the discovery and characterization of a new transiting planet from Campaign 17 of the Kepler extended mission K2. The planet K2-292 b is a warm sub-Neptune on a 17 day orbit around a bright (V = 9.9 mag) solar-like G3 V star with a mass and radius of M∗ = 1.00 ± 0.03 MȮ and R∗ = 1.09 ± 0.03 RȮ, respectively. We modeled simultaneously the K2 photometry and CARMENES spectroscopic data and derived a radius of Rp=2.63-0.10+0.12 RȮ and mass of Mp=24.5-4.4+4.4 MȮ, yielding a mean density of ρp=7.4-1.5+1.6 g cm-3, which makes it one of the densest sub-Neptunian planets known to date. We also detected a linear trend in the radial velocities of K2-292 (γRV =-0.40-0.07+0.07 m s-1 d-1) that suggests a long-period companion with a minimum mass on the order of 33 MȮ. If confirmed, it would support a formation scenario of K2-292 b by migration caused by Kozai-Lidov oscillations. © 2019 ESO. ; Funding for the K2 mission is provided by the NASA Science Mission directorate. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. CARMENES is an instrument for the Centro Astronomico Hispano-Aleman de Calar Alto (CAHA, Almeria, Spain) funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Cientificas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium. R.L. has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 713673 and financial support through the >la Caixa> INPhINIT Fellowship Grant for Doctoral studies at Spanish Research Centres of Excellence, >la Caixa> Banking Foundation, Barcelona, Spain. This work is partly financed by the Spanish Ministry of Economics and Competitiveness through grants ESP2013-48391-C4-2-R and AYA2016-79425-C3, and supported by the Japan Society for Promotion of Science (JSPS) KAKENHI Grant Number JP16K17660, JP18H01265 and JP18H05439, and JST PRESTO Grant Number JPMJPR1775. Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (Grant agreement no.: DNRF106). K.W.F.L acknowledges the support of the DFG priority program SPP 1992 >Exploring the Diversity of Exoplanets in the Mass-Density Diagram> (RA 714/14-1). M.F. and C.M.P. gratefully acknowledge the support of the Swedish National Space Agency. ; Peer Reviewed

The Transiting Exoplanet Survey Satellite, TESS, is currently carrying out an all-sky search for small planets transiting bright stars. In the first year of the TESS survey, a steady progress was made in achieving the mission's primary science goal of establishing bulk densities for 50 planets smaller than Neptune. During that year, the TESS's observations were focused on the southern ecliptic hemisphere, resulting in the discovery of three mini-Neptunes orbiting the star TOI-125, a V = 11.0 K0 dwarf. We present intensive HARPS radial velocity observations, yielding precise mass measurements for TOI-125b, TOI-125c, and TOI-125d. TOI-125b has an orbital period of 4.65 d, a radius of 2.726 ± 0.075 RE, a mass of 9.50 ± 0.88 ME, and is near the 2:1 mean motion resonance with TOI-125c at 9.15 d. TOI-125c has a similar radius of 2.759 ± 0.10 RE and a mass of 6.63 ± 0.99 ME, being the puffiest of the three planets. TOI-125d has an orbital period of 19.98 d and a radius of 2.93 ± 0.17 RE and mass 13.6 ± 1.2 ME. For TOI-125b and d, we find unusual high eccentricities of 0.19 ± 0.04 and 0.17^{+0.08}_{-0.06}, respectively. Our analysis also provides upper mass limits for the two low-SNR planet candidates in the system; for TOI-125.04 (RP = 1.36 RE, P = 0.53 d), we find a 2¿ upper mass limit of 1.6 ME, whereas TOI-125.05 (R_P=4.2^{+2.4}_{-1.4} RE, P = 13.28 d) is unlikely a viable planet candidate with an upper mass limit of 2.7 ME. We discuss the internal structure of the three confirmed planets, as well as dynamical stability and system architecture for this intriguing exoplanet system. ; With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)