An overabundance of low-density Neptune-like planets : научное издание

Тип публикации: статья из журнала

Год издания: 2017

Идентификатор DOI: 10.1093/mnras/stw3103

Ключевые слова: hydrodynamics, planets and satellites: atmospheres, planets and satellites: fundamental parameters

Аннотация: We present a uniform analysis of the atmospheric escape rate of Neptune-like planets with estimated radius and mass (restricted to Mp 30 M⊕). For each planet, we compute the restricted Jeans escape parameter, Λ, for a hydrogen atom evaluated at the planetary mass, radius, and equilibrium temperature. Values of Λ ≲ 20 suggest extremely high mass-loss rates. We identify 27 planets (out of 167) that are simultaneously consistent with hydrogen-dominated atmospheres and are expected to exhibit extreme mass-loss rates. We further estimate the mass-loss rates (Lhy) of these planets with tailored atmospheric hydrodynamic models. We compare Lhy to the energy-limited (maximum-possible high-energy driven) mass-loss rates. We confirm that 25 planets (15 per cent of the sample) exhibit extremely high mass-loss rates (Lhy 0.1 M⌖ Gyr−1), well in excess of the energy-limited mass-loss rates. This constitutes a contradiction, since the hydrogen envelopes cannot be retained given the high mass-loss rates. We hypothesize that these planets are not truly under such high mass-loss rates. Instead, either hydrodynamic models overestimate the mass-loss rates, transit-timing-variation measurements underestimate the planetary masses, optical transit observations overestimate the planetary radii (due to high-altitude clouds), or Neptunes have consistently higher albedos than Jupiter planets. We conclude that at least one of these established estimations/techniques is consistently producing biased values for Neptune planets. Such an important fraction of exoplanets with misinterpreted parameters can significantly bias our view of populations studies, like the observed mass–radius distribution of exoplanets for example.

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Журнал: Monthly Notices of the Royal Astronomical Society

Выпуск журнала: Т. 466, 2

Номера страниц: 1868-1879

ISSN журнала: 00358711

Издатель: John Wiley & Sons, Incorporated


  • Cubillos Patricio (Space Research Institute, Austrian Academy of Sciences)
  • Erkaev Nikolai V. (Krasnoyarsk Science Centre of the Siberian Branch of Russian Academy of Science)
  • Juvan Ines (Space Research Institute, Austrian Academy of Sciences)
  • Fossati Luca (Space Research Institute, Austrian Academy of Sciences)
  • Johnstone Colin P. (Department of Astrophysics, University of Vienna)
  • Lammer Helmut (Space Research Institute, Austrian Academy of Sciences)
  • Lendl Monika (Max Planck Institute for Astronomy)
  • Odert Petra (Space Research Institute, Austrian Academy of Sciences)
  • Kislyakova Kristina G. (Space Research Institute, Austrian Academy of Sciences)

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