Signatures of highly inclined accretion disks in Galactic Black Hole Candidates and AGNs

Abstract

Recent X-ray observations of Galactic Black Hole Candidates and AGNs and Seyfert galaxies reveal the broad emission lines in their spectra, which can arise in the innermost parts of accretion disks. Simulation indicates that at low inclination angle the line is registered by distant observer with characteristic two-peak profile. However, at high inclination angles ($> 85 \degr$) two additional peaks arise. This phenomenon was discovered by Matt, Perola, Stella (1993) using the Schwarzschild black hole metric to analyze such effect. They assumed that the effect is applicable to a Kerr metric far beyond of a range of parameters that they exploited. We check and confirm their hypothesis about such structure of the spectral line shape for a Kerr metric case. We use no astrophysical assumptions about physical structure of the emission region except assumption that the region should be narrow enough. Positions and heights of these extra peaks drastically depends on both the radial coordinate of the emitting region (circular hot spot) and the inclination angle. We find that best conditions to observe this effect are realized at $θ> 85\degr$ and $r > 5r_g$ and may exist in microquasars or low-mass black holes in X-ray binary systems, because there is some precession (and nutation of accretion disks) with not very long time periods (see, for example, SS433 binary system). The line profiles for different inclination angles and radial coordinates are presented. To analyze an influence of disk models on the spectral line shapes we simulate the line profiles for Shakura -- Sunyaev disk model for accretion disks with the high inclination.