Dynamical Tides in Highly Eccentric Binaries: Chaos, Dissipation and Quasi-Steady State

TL;DR

This paper investigates the complex dynamical behavior of tidal interactions in highly eccentric binary systems, revealing how mode excitation, chaos, and dissipation lead to orbital evolution and potential astrophysical phenomena.

Contribution

It introduces an iterative map model to analyze mode evolution, chaos, and dissipation in highly eccentric binaries, highlighting the emergence of a quasi-steady state and its astrophysical implications.

Findings

Modes exhibit low-amplitude, resonant, and chaotic growth behaviors.

Dissipation leads to a quasi-steady state with gradual orbital decay.

Chaotic mode growth can cause significant orbital changes in stars and planets.

Abstract

Highly eccentric binary systems appear in many astrophysical contexts, ranging from tidal capture in dense star clusters, precursors of stellar disruption by massive black holes, to high-eccentricity migration of giant planets. In a highly eccentric binary, the tidal potential of one body can excite oscillatory modes in the other during a pericenter passage, resulting in energy exchange between the modes and the binary orbit. These modes exhibit one of three behaviors over multiple passages: low-amplitude oscillations, large amplitude oscillations corresponding to a resonance between the orbital frequency and the mode frequency, and chaotic growth. We study these phenomena with an iterative map, fully exploring how the mode evolution depends on the pericenter distance and other parameters. In addition, we show that the dissipation of mode energy results in a quasi-steady state, with gradual orbital decay punctuated by resonances, even in systems where the mode amplitude would initially grow stochastically. A newly captured star around a black hole can experience significant orbital decay and heating due to the chaotic growth of the mode amplitude and dissipation. A giant planet pushed into a high-eccentricity orbit may experience a similar effect and become a hot or warm Jupiter.