Extensions of Brown Hamiltonian-II. Analytical study on the modified von Zeipel-Lidov-Kozai effects

TL;DR

This paper extends the Brown Hamiltonian to analyze modified von Zeipel-Lidov-Kozai effects in triple systems, providing analytical insights and validating them with numerical simulations, revealing asymmetries in ZLK characteristics.

Contribution

The work introduces an extended Hamiltonian framework and analytical expressions for ZLK oscillations, enhancing understanding of their dynamics in weakly hierarchical triple systems.

Findings

Analytical expressions match numerical results with high accuracy.

Librating and circulating cycles are separated by C_ZLK=0, consistent with classical theory.

ZLK characteristics exhibit asymmetry in prograde and retrograde regimes due to Brown corrections.

Abstract

In triple systems of weak hierarchies, nonlinear perturbations arising from the periodic oscillations associated with the inner and outer binaries play a crucial role in shaping their long-term dynamical evolution. In this context, we have developed an extended Brown Hamiltonian in Paper I, which serves as a fundamental model for describing the modified von Zeipel-Lidov-Kozai (ZLK) oscillations. The present work aims to analyze the characteristics of ZLK oscillations within this extended framework, focusing on phase-space structures, the location of ZLK center, the maximum eccentricity reached, the boundaries of librating cycles, and the critical inclination required to trigger ZLK resonance. Under the extended Hamiltonian, we introduce the Lidov integral C_ZLK, which is a combination of the Hamiltonian and the z-component of angular momentum, to characterize the modified ZLK properties. It is found that the librating and circulating cycles are separated by C_ZLK=0, which is consistent with the classical theory. Furthermore, we derive analytical expressions of these ZLK properties using perturbation techniques. Analytical predictions are compared to numerical results, showing an excellent agreement between them. Notably, the results reveal that ZLK characteristics in prograde and retrograde regimes are no longer symmetric under the influence of Brown corrections. At last, we conduct $N$-body integrations about millions of orbits to generate dynamical maps, where the numerical structures are well captured by the analytical solutions derived from the extended model.