A multi-parameter expansion for the evolution of asymmetric binaries in astrophysical environments

TL;DR

This paper introduces a multi-parameter formalism to model the evolution and gravitational wave emission of asymmetric binary systems embedded in matter distributions, extending vacuum perturbation theory to more realistic astrophysical environments.

Contribution

It develops a simplified, modular framework inspired by vacuum perturbation theory for modeling asymmetric binaries in matter-rich environments, applicable to most astrophysical scenarios.

Findings

The formalism captures the dynamics of binaries with matter distributions with radial and tangential pressures.

Wave equations for metric and fluid perturbations are closely related to vacuum cases in small deviation regimes.

The approach can be integrated with existing vacuum source models for realistic astrophysical predictions.

Abstract

Compact binaries with large mass asymmetries - such as Extreme and Intermediate Mass Ratio Inspirals - are unique probes of the astrophysical environments in which they evolve. Their long-lived and intricate dynamics allow for precise inference of source properties, provided waveform models are accurate enough to capture the full complexity of their orbital evolution. In this work, we develop a multi-parameter formalism, inspired by vacuum perturbation theory, to model asymmetric binaries embedded in general matter distributions with both radial and tangential pressures. In the regime of small deviations from the Schwarzschild metric, relevant to most astrophysical scenarios, the system admits a simplified description, where both metric and fluid perturbations can be cast into wave equations closely related to those of the vacuum case. This framework offers a practical approach to modeling the dynamics and the gravitational wave emission from binaries in realistic matter distributions, and can be modularly integrated with existing results for vacuum sources.