  Special and general relativistic effects on the X-ray emissions, especially
the continuum spectra, from the accretion disks around black holes are
investigated using the ray-tracing method. Because both the special and general
relativistic effects are more important at distances closer to the black hole,
the relativistic modifications to the emitted X-ray spectra are more
significant at higher energies. In a simple accretion disk precession model,
the relativistic effects can account for the energy dependence of the QPO
amplitude and phase-lags observed in several black hole binaries. The dramatic
QPO phase-lag transitions only show up when the central black hole is spinning
rapidly. The narrow distribution of the observed system inclination angles of
black hole binaries may be due to the selection effect caused by the
relativistic effects around black holes.
