  Young star clusters are often born with such high stellar densities that
stellar collisions play an important role in their further evolution. In such
environments the same star may participate in several tens to hundreds of
collisions ultimately leading to the collapse of the star to a black hole of
intermediate mass. At later time the black hole may acquire a companion star by
tidal capture or by dynamical --3-body-- capture. When this companion star
evolves it will fill its Roche-lobe and transfer mass to its accompanying black
hole. This then leads to a bright phase of X-ray emission but the binary may
also be visible as a source of gravitational wave radiation in the LISA band.
If the star captured by the intermediate mass black hole is relatively low mass
($\aplt 2$ \msun) the binary will be visible as a bright source in
gravitational waves and X-rays for the entire lifetime of the binary. The
majority of compact binaries which formed from the population of primordial
binaries in young and dense star clusters do not lead to detectable
gravitational wave sources.
