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

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  • D. Hidalgo, Instituto Astrofisico de Canarias
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  • E. Pallé, Instituto Astrofisico de Canarias, University of La Laguna
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  • R. Alonso, Instituto Astrofisico de Canarias, University of La Laguna
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  • R. Alonso, University of La Laguna
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  • D. Gandolfi, University of Turin
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  • G. Nowak, Instituto Astrofisico de Canarias, Chalmers University of Technology, Leiden University
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  • R. Luque, Instituto Astrofisico de Canarias, University of La Laguna
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  • R. Luque, University of La Laguna
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  • T. Hirano, Tokyo Institute of Technology
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  • A. B. Justesen
  • W. D. Cochran, University of Texas at Austin
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  • O. Barragán, University of Turin, University of Oxford
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  • L. Spina, Monash University
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  • F. Rodler, European Southern Observatory
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  • S. Albrecht
  • D. Anderson, University of Warwick
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  • P. Amado, CSIC - Institute of Astrophysics of Andalusia
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  • E. Bryant, CSIC - Institute of Astrophysics of Andalusia, University of Warwick
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  • J. A. Caballero, ?Astrobiology Center
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  • J. Cabrera, German Aerospace Center
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  • Sz Csizmadia, German Aerospace Center
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  • F. Dai, Massachusetts Institute of Technology, Princeton University
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  • H. J. Deeg, Instituto Astrofisico de Canarias, National Institutes of Natural Sciences - National Astronomical Observatory of Japan
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  • H. J. Deeg, University of La Laguna
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  • Ph Eigmuller, German Aerospace Center, Technical University of Berlin
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  • M. Endl, University of Texas at Austin
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  • A. Erikson, German Aerospace Center
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  • M. Esposito, Karl Schwarzschild Observatory
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  • P. Figueira, European Southern Observatory, University of Porto
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  • I. Georgieva, Chalmers University of Technology
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  • S. Grziwa, University of Cologne
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  • E. Guenther, Karl Schwarzschild Observatory
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  • A. P. Hatzes, Karl Schwarzschild Observatory
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  • M. Hjorth
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  • H. J. Hoeijmakers, University of Geneva, University of Bern
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  • P. Kabath, Czech Academy of Sciences
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  • J. Korth, University of Cologne
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  • M. Kuzuhara, National Institutes of Natural Sciences, National Institutes of Natural Sciences - National Astronomical Observatory of Japan
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  • M. Lafarga, Institute of Space Studies of Catalonia, Monash University
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  • M. Lampon, CSIC - Institute of Astrophysics of Andalusia
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  • I. C. Leão, Universidade Federal do Rio Grande do Norte
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  • J. Livingston, University of Tokyo
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  • S. Mathur, Instituto Astrofisico de Canarias, University of La Laguna
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  • P. Montañes-Rodriguez, Instituto Astrofisico de Canarias, University of La Laguna
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  • J. C. Morales, CSIC, Institute of Space Studies of Catalonia
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  • F. Murgas, Instituto Astrofisico de Canarias, University of La Laguna
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  • E. Nagel, University of Hamburg
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  • N. Narita, Instituto Astrofisico de Canarias, Japan Science and Technology Agency, National Institutes of Natural Sciences, National Institutes of Natural Sciences - National Astronomical Observatory of Japan
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  • L. D. Nielsen, Geneva Observatory, University of Geneva, Sauverny, Switzerland, University of Geneva
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  • M. Patzold, University of Cologne
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  • C. M. Persson, Chalmers University of Technology
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  • J. Prieto-Arranz, Instituto Astrofisico de Canarias, University of La Laguna
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  • A. Quirrenbach, Heidelberg University 
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  • H. Rauer, German Aerospace Center, Technical University of Berlin, Free University of Berlin
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  • S. Redfield, Wesleyan University
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  • A. Reiners, University of Göttingen
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  • I. Ribas, CSIC, Institute of Space Studies of Catalonia
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  • A. M.S. Smith, Institute for Planetary Research, DLR, German Aerospace Center
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  • J. Šubjak, Czech Academy of Sciences, Charles University
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  • V. Van Eylen, Mullard Space Science Laboratory, University College London, University College London
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  • P. A. Wilson, University of Warwick

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.

OriginalsprogEngelsk
ArtikelnummerA89
TidsskriftAstronomy and Astrophysics
Vol/bind636
Antal sider13
ISSN0004-6361
DOI
StatusUdgivet - apr. 2020

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