Signatures of highly inclined accretion disks in galactic black hole candidates and AGNs

Abstract

Recent X-ray observations of microquasars and Seyfert galaxies reveal broad emission lines in their spectra, which can arise in the innermost parts of accretion disks. Simulations indicate that at low inclination angle the line is measured by a distant observer as characteristic two-peak profile. However, at high inclination angles (>$ 85 \degr$) two additional peaks arise. This phenomenon was discovered by [CITE] using the Schwarzschild black hole metric to analyze such effect. They assumed that the effect is applicable to a Kerr metric far beyond the range of parameters that they exploited. We check and confirm their hypothesis about such a structure of the spectral line shape for the Kerr metric case. We use no astrophysical assumptions about the physical structure of the emission region except the assumption that the region should be narrow enough. Positions and heights of these extra peaks drastically depend on both the radial coordinate of the emitting region (circular hot spot) and the inclination angle. We find that the best conditions to observe this effect are realized at $\theta > 85\degr$ and $r > 5r_{\rm g}$ 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, the SS433 binary system). The line profiles for different inclination angles and radial coordinates are presented. To analyze the influence of disk models on the spectral line shapes we simulate the line profiles for the Shakura–Sunyaev disk model for accretion disks with the high inclination.