Effects of black hole environments on extreme mass-ratio hyperbolic encounters

TL;DR

This paper investigates how surrounding matter, like accretion disks and dark matter spikes, influences the orbital dynamics and gravitational wave signals of extreme mass-ratio hyperbolic encounters near supermassive black holes, highlighting potential observational signatures.

Contribution

It provides the first detailed analysis of environmental effects on EMRHEs and their gravitational waveforms, emphasizing the impact of accretion disks and the subtlety of dark matter influences.

Findings

Accretion disks significantly affect orbital evolution and waveforms.

Dark matter spikes have a minimal impact on gravitational wave signals.

Environmental effects may leave detectable imprints, but are challenging to resolve with upcoming detectors.

Abstract

Extreme mass-ratio hyperbolic encounters (EMRHEs) around the supermassive black holes will be observable at the future gravitational-wave (GW) detectors in space, such as LISA and Taiji. Here we consider such EMRHEs in the presence of surrounding matter distribution including baryonic accretion disk and dark matter (DM) spike, and estimate their effects on the orbital evolution and GW waveforms. We find that large possible impacts come from the gravitational potential of accretion disk, while the influence of DM spike is small. We also illustrate that environments can leave distinctive imprints on the GW waveforms, but resolving such modifications is found to be challenging for LISA-like detectors in the near future.