The Astrophysical Journal (Jan 2025)

Planet–Planet Scattering and Von Zeipel–Lidov–Kozai Migration—The Dynamical History of HAT-P-11

  • Tiger Lu,
  • Qier An,
  • Gongjie Li,
  • Sarah C. Millholland,
  • Malena Rice,
  • G. Mirek Brandt,
  • Timothy D. Brandt

DOI
https://doi.org/10.3847/1538-4357/ad9b79
Journal volume & issue
Vol. 979, no. 2
p. 218

Abstract

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The two planets of the HAT-P-11 system represent fascinating dynamical puzzles due to their significant eccentricities and orbital misalignments. In particular, HAT-P-11 b is in a close-in orbit in which tides should have circularized well within the age of the system. Here we propose a two-step dynamical process that can reproduce all intriguing aspects of the system. We first invoke planet–planet scattering to generate significant eccentricities and mutual inclinations between the planets. We then propose that this misalignment initiated von-Zeipel-Lidov-Kozai cycles and high-eccentricity migration that ultimately brought HAT-P-11 b to its present-day orbit. We find that this scenario is fully consistent only when significant tidally driven radius inflation is accounted for during the tidal migration. We present a suite of N -body simulations exploring each phase of evolution and show that this scenario is consistent with all observational posteriors and the reported age of the system.

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