The Orbital Eccentricity of Small Planet Systems

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  • Vincent Van Eylen, Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08540, USA, Leiden Observatory, Leiden University, NL-2333CA Leiden, The Netherlands, Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark., vaneylen@astro.princeton.edu 0000-0001-5542-8870
  • ,
  • Simon Albrecht
  • Xu Huang, MIT Kavli Institute for Astrophysics and Space Research, 70 Vassar St., Cambridge, MA 02139, USA
  • ,
  • Mariah G. MacDonald, Department of Astronomy & Astrophysics, and Center for Exoplanets and Habitable Worlds, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802, USA 0000-0003-2372-1364
  • ,
  • Rebekah I. Dawson, Department of Astronomy & Astrophysics, and Center for Exoplanets and Habitable Worlds, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802, USA 0000-0001-9677-1296
  • ,
  • Maxwell X. Cai, Leiden Observatory, Leiden University, 2333CA Leiden, The Netherlands 0000-0002-1116-2705
  • ,
  • Daniel Foreman-Mackey, Center for Computational Astrophysics, Flatiron Institute, 162 Fifth Avenue, New York, NY 10010, USA 0000-0002-9328-5652
  • ,
  • Mia S. Lundkvist
  • Victor Silva Aguirre
  • Ignas Snellen, Leiden Observatory, Leiden University, NL-2333CA Leiden, The Netherlands
  • ,
  • Joshua N. Winn, Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08540, USA 0000-0002-4265-047X
We determine the orbital eccentricities of individual small Kepler planets, through a combination of asteroseismology and transit light-curve analysis. We are able to constrain the eccentricities of 51 systems with a single transiting planet, which supplement our previous measurements of 66 planets in multi-planet systems. Through a Bayesian hierarchical analysis, we find evidence that systems with only one detected transiting planet have a different eccentricity distribution than systems with multiple detected transiting planets. The eccentricity distribution of the single-transiting systems is well described by the positive half of a zero-mean Gaussian distribution with a dispersion σ e = 0.32 ± 0.06, while the multiple-transit systems are consistent with {σ }e={0.083}-0.020+0.015. A mixture model suggests a fraction of {0.76}-0.12+0.21 of single-transiting systems have a moderate eccentricity, represented by a Rayleigh distribution that peaks at {0.26}-0.06+0.04. This finding may reflect differences in the formation pathways of systems with different numbers of transiting planets. We investigate the possibility that eccentricities are self-excited in closely packed planetary systems, as well as the influence of long-period giant companion planets. We find that both mechanisms can qualitatively explain the observations. We do not find any evidence for a correlation between eccentricity and stellar metallicity, as has been seen for giant planets. Neither do we find any evidence that orbital eccentricity is linked to the detection of a companion star. Along with this paper, we make available all of the parameters and uncertainties in the eccentricity distributions, as well as the properties of individual systems, for use in future studies.
Original languageEnglish
JournalThe Astronomical Journal
Volume157
Issue2
Pages (from-to)61
ISSN0004-6256
DOIs
Publication statusPublished - 1 Feb 2019
Externally publishedYes

    Research areas

  • planets and satellites: dynamical evolution and stability, planets and satellites: formation, planets and satellites: fundamental parameters, planets and satellites: terrestrial planets, stars: oscillations: including pulsations

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