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Session 100 - Accretion Disks and Black Holes.
Display session, Thursday, January 16
In regions where electron scattering dominates the opacity above accretion disks, X-ray radiation originating there should be partially linearly polarized. Both observations of rapid X-ray variability and theoretical studies suggest that this inner disk region is unstable and could appear clumpy. We investigate polarization features due to orbiting bright spots around a black hole. In particular, we examine how variations in the orbital parameters of the bright spots and the angle between the line of sight and the disk axis affect the observed polarization.
Unlike in the Newtonian case, rapid polarization variability can be produced by these bright spots and the variability amplitudes of both the degree of polarization and the angle of the plane of polarization are energy-dependent. Explicitly, the amplitude of the polarization variability is expected to be larger at higher energies. This feature is directly created by the gravitational bending of light rays by the central black hole and it is apparently unique to a system including a black hole and an accretion disk. Since accretion disks around black holes are expected for both active galactic nuclei and in galactic X-ray binaries, future X-ray polarimetry missions could test our predictions.
This work was supported in part by NASA grant NAG 5-3098.
Program listing for Thursday