Low Frequency Gravitational Waves from Black Hole MACHO Binaries

TL;DR

This paper models the low-frequency gravitational wave background from primordial black hole MACHO binaries in the galactic halo, predicting a strong stochastic signal detectable by space-based interferometers like LISA.

Contribution

It provides the first detailed calculation of the low-frequency gravitational wave spectrum from MACHO binaries, linking dark matter candidates to observable gravitational wave signals.

Findings

Predicted a strong stochastic gravitational wave background in the 10^{-5} to 10^{-1} Hz range.

Showed that space-based detectors could probe the properties of dark matter MACHO binaries.

Highlighted the importance of low-frequency gravitational waves in understanding dark matter populations.

Abstract

Nakamura, Sasaki, Tanaka, and Thorne have recently estimated the initial distribution of binary MACHOs in the galactic halo assuming that the MACHOs are primordial half solar mass black holes, and considered their coalescence as a possible source for ground-based interferometer gravitational wave detectors such as LIGO. Evolving their binary distribution forward in time to the present, the low-frequency (10^{-5} < f < 10^{-1} Hz) spectrum of gravitational waves associated with such a population of compact binaries is calculated. The resulting gravitational waves would form a strong stochastic background in proposed space interferometers such as LISA and OMEGA. Low frequency gravitational waves are likely to become a key tool for determining the properties of binaries within the dark MACHO population.