Binary Black Holes in Stationary Orbits
  We show that under certain astrophysical conditions a binary system consisting of two compact objects can be stabilized against indefinite shrinking of orbits due to the emission of gravitational radiation. In this case, the lighter binary companion settles down to a stable orbit when the loss of the angular momentum due to gravitational radiation becomes equal to its gain from the accreting matter from the disk around the more massive primary. We claim that such systems can be stable against small perturbations and can be regarded as steady emitters of gravitational waves of constant frequency and amplitude. Furthermore, X-rays emitted by the secondary can also produce astrophysically interesting situations when coupled with gravitational lensing and Doppler effects. 
Sandip K. Chakrabarti (Tata Institute of Fundamental Research, Bombay,   INDIA)