We develop a method of calculating the X-ray signal from a "spot" corotating with an accretion disk around a black hole and the emission line from the X-ray-illuminated disk. The disk self-eclipse is considered, and all effects of general relativity on the motion of photons are included with no approximation. The eclipse strongly affects the shape of the X-ray light curve of the spot and the K fluorescent line irradiated by the disk. The FWHM and strength of the line profile are reduced significantly if the eclipsed region of the orbit is very deep. For a given radius of a ring in the disk, this occurs when the eclipsed region of the orbit is deeper than π/2. The centroid of a line profile is also subject to the eclipse effect.
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We develop a method of calculating the X-ray signal from a 'spot'
corotating with an accretion disk around a black hole and the emission
line from the X-ray-illuminated disk. The disk self-eclipse is
considered, and all effects of general relativity on the motion of
photons are included with no approximation. The eclipse strongly affects
the shape of the X-ray light curve of the spot and the K fluorescent
line irradiated by the disk. The FWHM and strength of the line profile
are reduced significantly if the eclipsed region of the orbit is very
deep. For a given radius of a ring in the disk, this occurs when the
eclipsed region of the orbit is deeper than pi/2. The centroid of a line
profile is also subject to the eclipse effect.
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The general-relativistic effects of an extreme Reissner-Nordström black hole on the flux of radiation emitted by a hot spot orbiting the hole with a thin accretion disk are investigated. The light curves, the redshift factor, and the solid angle against the spot orbit position are given. The results are then compared with those of a spot orbiting a Schwarzschild black hole.
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The general-relativistic effects of an extreme Reissner-Nordström
black hole on the flux of radiation emitted by a hot spot orbiting the
hole with a thin accretion disk are investigated. The light curves, the
redshift factor, and the solid angle against the spot orbit position are
given. The results are then compared with those of a spot orbiting a
Schwarzschild black hole.
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We study the radial motion along null geodesics in the Reissner-Nordström-de Sitter and Kerr-de Sitter space-times. We analyze the properties of the effective potential and we discuss circular orbits. We find that: 1) the radius of circular photon orbits in the Reissner-Nordström-de Sitter space-times does not depend on the cosmological constant. We show also how this is related to properties of the optical reference geometry. 2) For a specific range of the cosmological constant, photons with high impact parameter may travel radially between the cosmological horizon and the black hole horizon in the equatorial plane of the Kerr-de Sitter space-times.
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We study the radial motion along null geodesics in the
Reissner-Nordström-de Sitter and Kerr-de Sitter space-times. We
analyze the properties of the effective potential and we discuss
circular orbits. We find that:
1)
the radius of circular photon orbits in the Reissner-Nordström-de
Sitter space-times does not depend on the cosmological constant. We show
also how this is related to properties of the optical reference
geometry.
2)
For a specific range of the cosmological constant, photons with high
impact parameter may travel radially between the cosmological horizon
and the black hole horizon in the equatorial plane of the Kerr-de Sitter
space-times.
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The static region of the Schwarzschild-de Sitter spacetime is studied from the point of view of the optical reference geometry introduced by Abramowicz et al. (1988). It is shown that, in this geometry, the geodesic curvature of circles r = const is independent of the parameter Lambda (cosmological constant) of the spacetime. The consequence of this fact for circular photon orbits is discussed.
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The static region of the Schwarzschild-de Sitter spacetime is studied
from the point of view of the optical reference geometry introduced by
Abramowicz et al. (1988). It is shown that, in this geometry, the
geodesic curvature of circles r = const is independent of the parameter
Lambda (cosmological constant) of the spacetime. The consequence of this
fact for circular photon orbits is discussed.
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