Gravitational Waves from Coalescing Black Hole Macho Binaries

If MACHOs are black holes of mass ∼0.5 M,, they must have been formed in the early universe when the temperature was ∼1 GeV. We estimate that in this case in our Galaxy’s halo out to ∼ 50 kpc there exist ∼5 # black hole binaries the coalescence times of which are comparable to the age of the universe, so that the 8 10 coalescence rate will be ∼ events yr per galaxy. This suggests that we can expect a few events per 22 5 # 10 year within 15 Mpc. The gravitational waves from such coalescing black hole MACHOs can be detected by the first generation of interferometers in the LIGOZVIRGOZTAMAZGEO network. Therefore, the existence of black hole MACHOs can be tested within the next 5 yr by gravitational waves. Subject headings: black hole physics — dark matter — gravitation — gravitational lensing — Galaxy: halo