Extensions of Brown Hamiltonian-III. Applications to irregular satellites of giant planets

TL;DR

This paper extends the Brown Hamiltonian framework to irregular satellites, introducing the modified Lidov integral ($C_{ m ZLK}$) as a diagnostic for ZLK resonance, validated by simulations.

Contribution

It introduces the $C_{ m ZLK}$ index for identifying ZLK resonance in irregular satellites, enhancing analysis of their secular dynamics.

Findings

$C_{ m ZLK}$ accurately predicts 26 out of 27 libration candidates.

Direct N-body simulations confirm the effectiveness of the $C_{ m ZLK}$ criterion.

The index helps analyze weakly hierarchical three-body systems.

Abstract

Irregular satellites, orbiting at large distances from their host planets, are subject to strong solar perturbations that render long-term orbital predictions particularly challenging. Building upon the extended Brown Hamiltonian framework developed in Paper I, we introduce the modified Lidov integral ($C_{\rm ZLK}$) as a practical diagnostic index to characterize the dynamical modes. We demonstrate that a satellite is trapped inside the von Zeipel--Lidov--Kozai (ZLK) resonance when $C_{\rm ZLK} < 0$. Applying this criterion to the known population of irregular satellites, we identify 27 candidates in libration. Direct $N$-body simulations confirm 26 of these predictions, with the sole exception of S/2019 S1, whose discrepancy is attributed to its proximity to the separatrix. These results establish $C_{\rm ZLK}$ as a decisive parameter for identifying the ZLK resonance, providing an efficient tool for analyzing the secular dynamics in weakly hierarchical three-body systems.