Relativistic Effects on X-ray Emissions from Accretion Disks around Black Holes

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.