A Direct Probe of Mass Density Near Inspiraling Binary Black Holes

TL;DR

This paper proposes that future space-based gravitational wave detectors like LISA could detect environmental effects on binary black hole signals, revealing the ambient mass density near inspiraling binaries.

Contribution

It introduces a method to directly probe the mass density around binary black holes through observable waveform modifications in gravitational wave signals.

Findings

Potential to measure ambient mass density via waveform phase shifts

Detectable Doppler shifts in gravitational wave signals from environmental interactions

Future detectors like LISA can provide insights into black hole environments

Abstract

Now that LIGO has revealed the existence of a large number of binary black holes, identifying their origin becomes an important challenge. They might originate in more isolated regions of the galaxy or alternatively they might reside in dense environments such as galactic centers or globular clusters. In the latter case, their center of mass motion as well as their orbital parameters should lead to observable changes in the waveforms, which would reflect their gravitational interactions with the surrounding matter. This would be reflected in the gravitational wave signal by a net phase change or even a time-dependent Doppler shift. We show that this time-dependence might be observable in future space gravitational wave detectors such as LISA which could provide direct information about the black hole binary environments and otherwise invisible ambient mass.