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

By V. Van Eylen, Camilla Agentoft, M. Lundkvist, H. Kjeldsen, J. Owen, B. Fulton, E. Petigura, I. Snellen. Monthly notices of the Royal Astronomical Society, 2017

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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 ≈2R⊕. 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 (≈1.5R⊕) and sub-Neptunes (≈2.5 R⊕) separated by a deficiency around 2R⊕. We furthermore characterize the slope of the valley as a power law R∝Pγ with γ=−0.09^(+0.02)_(−0.04). 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.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/0a877cedafafe6012c689eff549eab614cb155b4

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In Astronomy and Astrophysics

  1. D. Huber
  2. J. V. van Saders
  3. T. Berger
  4. E. Gaidos
  5. L. Weiss
  6. A. Mann
  7. E. Petigura
  8. Leslie A. Rogers

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