Suppression of extreme orbital evolution in triple systems with short range forces

TL;DR

This paper investigates how short-range forces like General Relativity and tidal effects suppress extreme eccentricity and orbital flips in triple systems undergoing octupole-level Lidov-Kozai cycles, refining understanding of their dynamical evolution.

Contribution

It provides a systematic analysis of the impact of short-range forces on octupole LK cycles, including an analytical expression for the maximum eccentricity and the conditions for orbital flips.

Findings

Short-range forces limit maximum eccentricity achievable in octupole LK cycles.

These forces reduce the parameter space for orbital flips as their strength increases.

The maximum eccentricity limit is analytically derived and applicable to various mass configurations.

Abstract

The Lidov-Kozai (LK) mechanism plays an important role in the secular evolution of many hierarchical triple systems. The standard LK mechanism consists of large-amplitude oscillations in eccentricity and inclination of a binary subject to the quadrupole potential from an outer perturber. Recent work has shown that when the octupole terms are included in the potential, the inner binary can reach more extreme eccentricities as well as undergo orientation flips. It is known that pericenter precessions due to short-range effects, such as General Relativity and tidal and rotational distortions, can limit the growth of eccentricity and even suppress standard (quadrupolar) LK oscillations, but their effect on the octupole-level LK mechanism has not been fully explored. In this paper, we systematically study how these short-range forces affect the extreme orbital behaviour found in octupole LK cycles. In general, the influence of the octupole potential is confined to a range of initial mutual inclinations Itot centered around 90deg (when the inner binary mass ratio is <<1), with this range expanding with increasing octupole strength. We find that, while the short-range forces do not change the width and location of this "window of influence", they impose a strict upper limit on the maximum achievable eccentricity. This limiting eccentricity can be calculated analytically, and its value holds even for strong octupole potential and for the general case of three comparable masses. Short-range forces also affect orbital flips, progressively reducing the range of Itot within which flips are possible as the intensity of these forces increases.