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Paper: Spectral and Temporal Variability Incorporating General Relativistic Effects
Volume: 159, BL Lac Phenomenon
Page: 483
Authors: Wiita, Paul J.; Bao, Gang
Abstract: Composite spectra, including contributions from an accretion disk around a black hole, a primary X-ray power-law source, and the photons reflected from the disk, are considered in Schwarzschild geometry. The strength, shape and broadening of the reflected spectrum depend on the directions of the X-ray source relative to the disk and the observer's viewing angle. The reflection hump can essentially disappear if viewed far from the symmetry axis as the X-ray photons are affected by gravity both approaching and leaving the disk. As the innermost part of accretion disks are expected to be unstable and clumpy, some of the X-ray variability can be due to motions of these regions orbiting the black hole. Even for face-on geometries, rotation induced variability can be observed as long as the non-thermal source is not exactly on the symmetry axis.
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