Low-Frequency Gravitational Waves from Black Hole MACHO Binaries

Nakamura, Sasaki, Tanaka, and Thorne have recently estimated the initialdistribution of binary MACHOs in the galactic halo assuming that the MACHOs areprimordial half solar mass black holes, and considered their coalescence as apossible source for ground-based interferometer gravitational wave detectorssuch as LIGO. Evolving their binary distribution forward in time to thepresent, the low-frequency (10^{-5} < f < 10^{-1} Hz) spectrum of gravitationalwaves associated with such a population of compact binaries is calculated. Theresulting gravitational waves would form a strong stochastic background inproposed space interferometers such as LISA and OMEGA. Low frequencygravitational waves are likely to become a key tool for determining theproperties of binaries within the dark MACHO population.Comment: 8 pages + 2 ps figures; AASTe