  To complement hydrodynamic studies of the tidal disruption of the star by a
massive black hole, we present the study of stellar luminosity and its
variations, produced by the strong gravitational field of the black hole during
a close encounter. By simulating the relativistically moving star and its
emitted light and taking into account general relativistic effects on particle
and light trajectories, our results show that the black hole's gravity alone
induces apparent stellar luminosity variations on typical timescales of a few
r_g/c (=5 sec m_bh/10^6 M_\odot) to a few 100 r_g/c (\sim 10 min m_bh/10^6
M_\odot), where r_g=Gm_bh/c^2. We discern different cases with respect to the
strength of tidal interaction and focus on two: a) a star encountering a giant
black hole traces space-time almost as a point particle, so that the apparent
luminosity variations are dominated by clearly recognizable general
relativistic effects and b) in a close encounter of a star with a black hole of
similar size the stellar debris is spread about the black hole by processes
where hydrodynamics plays an important role. We discuss limitations and results
of our approach.
