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K2-265 b: a transiting rocky super-Earth

K. W. F. Lam, A. Santerne, S. G. Sousa, A. Vigan, D. J. Armstrong, S. C. C. Barros, B. Brugger, V. Zh. Adibekyan, J.-M. Almenara, E. Delgado Mena, X. Dumusque, D. Barrado, D. Bayliss, A. S. Bonomo, F. Bouchy, D. Brown, D. Ciardi, M. Deleuil, O. Demangeon, F. Faedi, E. Foxell, J. Jackman, G. King, J. Kirk, R. Ligi, J. Lillo Box, T. Lopez, C. Lovis, T. Louden, L. D. Nielsen, J. McCormac, O. Mousis, H. P. Osborn, D. Pollacco, N. C. Santos, S. Udry, P. J. Wheatley

Abstract
We report the discovery of the super-Earth K2-265 b detected with K2 photometry. The planet orbits a bright (Vmag = 11.1) star of spectral type G8V with a period of 2.37 days. We obtained high-precision follow-up radial velocity measurements from HARPS, and the joint Bayesian analysis showed that K2-265 b has a radius of 1.71 ± 0.11 R and a mass of 6.54 ± 0.84 M, corresponding to a bulk density of 7.1 ± 1.8 g cm−3. Composition analysis of the planet reveals an Earth-like, rocky interior; this object has a rock mass fraction of ~80%. The short orbital period and small radius of the planet puts it below the lower limit of the photoevaporation gap, where the envelope of the planet could have eroded owing to strong stellar irradiation, leaving behind an exposed core. Knowledge of the planet core composition allows us to infer the possible formation and evolution mechanism responsible for its current physical parameters.

Keywords
techniques: photometric; techniques: radial velocities; planets and satellites: detection; stars: individual: K2-265; planets and satellites: composition; Astrophysics - Earth and Planetary Astrophysics

Astronomy and Astrophysics
Volume 620, Article Number A77, Number of pages 13
2018 December

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Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia