Why do warm Neptunes present nonzero eccentricity?

@article{Correia2020WhyDW,
  title={Why do warm Neptunes present nonzero eccentricity?},
  author={Alexandre C. M. Correia and Vincent Bourrier and Jean-Baptiste Delisle},
  journal={arXiv: Earth and Planetary Astrophysics},
  year={2020}
}
Most Neptune-mass planets in close-in orbits (orbital periods less than a few days) present nonzero eccentricity, typically around 0.15. This is somehow unexpected, as these planets undergo strong tidal dissipation that should circularize their orbits in a time-scale shorter than the age of the system. In this paper we discuss some mechanisms that can oppose to bodily tides, namely, thermal atmospheric tides, evaporation of the atmosphere, and excitation from a distant companion. In the first… Expand

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