New Twists In The Study Of Gravity Wave Emission In Systems With Massive   Black Holes
  Traditionlly, gravitational wave emission from a coalescing binary system is computed using point mass approximations without considering any accretion disk. However, it is believed that in many of the galactic nuclei, there are supermassive central black holes surrounded by accretion disks. These accretion disks must be necessarily supersonic on and outside the horizon simply because the radial velocity (in the corotating frame) has to be the velocity of light on the horizon while the sound speed must be smaller. However, supersonic flows are typically sub-Keplerian. Thus, smaller black holes and neutron stars (which are on instantaneously Keplerian orbit and lose energy and angular momentum through gravitational radiation) on their way to coalesce with the central black hole must accrete negative angular momentum from the disk. We study here the way these disks affect the gravitational wave emission. 
Sandip K. Chakrabarti