Black hole MACHO and its identification

If MACHOs are primordial black holes of mass similar to 0.5M. (BHMACHO), it is extremely difficult, if not impossible, to identify BHMACHOs by their accretion-driven emission. However using gravitational wave detectors, BHMACHOs may be identified. There may exist similar to 5 x 10(8) BHMACHO binaries in the halo up to similar to 50 kpc whose coalescing time due to the emission of gravitational waves is comparable to the age of the universe. This means that the event rate will be similar to 5 x 10(-2) events/yr/galaxy and several events/yr within 15 Mpc are expected. The gravitational waves from such coalescing BHMACHO binaries, if they exist, can be detected by LIGO, VIRGO, TAMA and GEO within next 5 years. (C) 1998 Elsevier Science B.V. All rights reserved.