• DOI:10.1051/0004-6361/201937080
• Corpus ID: 211032193

Three planets transiting the evolved star EPIC 249893012: a hot 8.8-M⊕ super-Earth and two warm 14.7 and 10.2-M⊕ sub-Neptunes

@article{Hidalgo2020ThreePT,
  title={Three planets transiting the evolved star EPIC 249893012: a hot 8.8-M⊕ super-Earth and two warm 14.7 and 10.2-M⊕ sub-Neptunes},
  author={Diego Hidalgo and Enric Pall{\'e} and Ricardo J. Alonso and Davide Gandolfi and Malcolm Fridlund and Grzegorz Nowak and Rafael Luque and Teruyuki Hirano and Anders B. Justesen and William D. Cochran and Oscar Barragan and Lorenzo Spina and Florian Rodler and Simon H. Albrecht and D. R. Anderson and Pedro J. Amado and Edward M. Bryant and Jos{\'e} A. Caballero and Juan Cabrera and Sz. Csizmadia and Fei Dai and Jerome P. de Leon and Hans J. Deeg and Philipp Eigmuller and Michael Endl and Anders Erikson and Massimiliano Esposito and Pedro Figueira and I. Georgieva and Sascha Grziwa and E. W. Guenther and A. P. Hatzes and Maria Hjorth and H. Jens Hoeijmakers and Petr Kab{\'a}th and J. Korth and Masayuki Kuzuhara and Marina Lafarga and Manuel Lamp{\'o}n and I. C. Le{\~a}o and John H. Livingston and Savita Mathur and Pilar Monta{\~n}{\'e}s-Rodr{\'i}guez and J. C. Morales and Felipe Murgas and Evangelos Nagel and Norio Narita and Louise D. Nielsen and Martin Patzold and Carina M. Persson and Jorge Prieto-arranz and Andreas Quirrenbach and Heike Rauer and Seth Redfield and Ansgar Reiners and Ignasi Ribas and A M S Smith and J{\'a}n {\vS}ubjak and Vincent Van Eylen and Paul A. Wilson},
  journal={Astronomy \& Astrophysics},
  year={2020}
}

• D. Hidalgo, E. Pallé, +57 authors P. Wilson
• Published 5 February 2020
• Physics, Geology
• Astronomy & Astrophysics

We report the discovery of a new planetary system with three transiting planets, one super-Earth and two sub-Neptunes, that orbit EPIC 249893012, a G8 IV-V evolved star (M⋆ = 1.05 ± 0.05 M⊙, R⋆ = 1.71 ± 0.04 R⊙, Teff = 5430 ± 85 K). The star is just leaving the main sequence. We combined K2 photometry with IRCS adaptive-optics imaging and HARPS, HARPS-N, and CARMENES high-precision radial velocity measurements to confirm the planetary system, determine the stellar parameters, and measure radii, masses, and densities of the three planets. With an orbital period of 3.5949−0.0007+0.0007 days, a mass of 8.75−1.08+1.09 M⊕, and a radius of 1.95−0.08+0.09 R⊕, the inner planet b is compatible with nickel-iron core and a silicate mantle (ρb = 6.39−1.04+1.19 g cm−3). Planets c and d with orbital periods of 15.624−0.001+0.001 and 35.747−0.005+0.005 days, respectively, have masses and radii of 14.67−1.89+1,84 M⊕ and 3.67−0.14+0.17 R⊕ and 10.18−2.42+2.46 M⊕ and 3.94−0.12+0.13 R⊕, respectively, yielding a mean density of 1.62−0.29+0.30 and 0.91−0.23+0.25 g cm−3, respectively. The radius of planet b lies in the transition region between rocky and gaseous planets, but its density is consistent with a rocky composition. Its semimajor axis and the corresponding photoevaporation levels to which the planet has been exposed might explain its measured density today. In contrast, the densities and semimajor axes of planets c and d suggest a very thick atmosphere. The singularity of this system, which orbits a slightly evolved star that is just leaving the main sequence, makes it a good candidate for a deeper study from a dynamical point of view.