An asteroseismic view of the radius valley: stripped cores, not born rocky

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DOI

  • V. Van Eylen, Leiden Univ, Leiden University, Leiden Observ
  • ,
  • Camilla Agentoft
  • M. S. Lundkvist
  • H. Kjeldsen
  • J. E. Owen, Imperial Coll London, Blackett Lab, Astrophys Grp
  • ,
  • B. J. Fulton, CALTECH, California Institute of Technology, Div Geol & Planetary Sci
  • ,
  • E. Petigura, CALTECH, California Institute of Technology, Div Geol & Planetary Sci
  • ,
  • I. Snellen, Leiden Univ, Leiden University, Leiden Observ

Various theoretical models treating the effect of stellar irradiation on planetary envelopes predict the presence of a radius valley, i.e. a bimodal distribution of planet radii, with super-Earths and sub-Neptune planets separated by a valley at around approximate to 2R(circle plus) Such a valley has been observed recently, owing to an improvement in the precision of stellar and therefore planetary radii. Here, we investigate the presence, location, and shape of such a valley using a small sample with highly accurate stellar parameters determined from asteroseismology, which includes 117 planets with a median uncertainty on the radius of 3.3 per cent. We detect a clear bimodal distribution, with super-Earths (approximate to 1.5R(circle plus))and sub-Neptunes (approximate to 2.5R(circle plus)) separated by a deficiency around 2R(circle plus). We furthermore characterize the slope of the valley as a power law R proportional to P-gamma with gamma = -0.09(-0.04)(+0.02). A negative slope is consistent with models of photoevaporation, but not with the late formation of rocky planets in a gas-poor environment, which would lead to a slope of opposite sign. The exact location of the gap further points to planet cores consisting of a significant fraction of rocky material.

Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Volume479
Issue4
Pages (from-to)4786-4795
Number of pages10
ISSN0035-8711
DOIs
Publication statusPublished - Oct 2018

    Research areas

  • planets and satellites: composition, planets and satellites: formation, planets and satellites: fundamental parameters, planets and satellites: physical evolution, SUPER-EARTHS, HOST STARS

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