  The possibility that some Markarian objects (e.g. Mkn 501, Mkn 421 and Mkn
766) host massive binary black hole systems with eccentric orbits at their
centers has been considered. These systems could be sources of gravitational
radiation for space-based gravitational wave interferometers like LISA and
ASTROD. In the framework of the Lincoln -- Will approximation we simulate
coalescence of such systems, calculate gravitational wave templates and discuss
parameters of these binary black hole systems corresponding to the facilities
of LISA and ASTROD. We discuss also the possibility to extract information
about parameters of the binary black hole systems (masses, of components,
distances between them, eccentricity and orbit inclination angle with respect
to line of sight) from future gravitational wave measurements.
