Tests of General Relativity in the Strong Gravity Regime With the Space-Borne X-Calibur X-ray Polarimeter
Abstract
Broadband spectropolarimetric observations of black holes in X-ray binaries with X-Calibur will allow us to test General Relativity in the yet untested strong gravity regime. We study the spectral and polarimetric signatures with two models. First we model a hot spot in the accretion disk of a black hole. This is then used to explain the position and amplitude of the high frequency quasi periodic oscillations (HFQPO) peaks. These HFQPOs have been repeatedly observed at near constant frequencies however their origin is still unknown. The second model uses a lamp-post to illuminate the accretion disk with high-energy photons. Photons acquire a polarization when scattering in the disk. We have developed a code that parallel transports the photon wave and polarization vectors through the Kerr spacetime or alternative spacetimes. Furthermore, it models the polarization changes from photon reflections off the accretion disk with the formalism of Chandrasekhar (1950). The numerical simulations allow us to evaluate how well X-Calibur can constrain the black hole spin and the accretion disk inclination. Furthermore, we are able to assess the impact of alternative spacetimes on the observable flux and polarization energy spectra.
- Publication:
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AAS/High Energy Astrophysics Division #14
- Pub Date:
- August 2014
- Bibcode:
- 2014HEAD...1411613H