X-ray Polarization from Black Holes in the Thermal State
arXiv:0906.0559 · doi:10.1017/CBO9780511750809.015
Abstract
We present new calculations of X-ray polarization from black hole accretion disks in the thermally-dominated state, using a Monte-Carlo ray-tracing code in full general relativity. In contrast to many previously published studies, our approach allows us to include returning radiation that is deflected by the strong-field gravity of the BH and scatters off of the disk before reaching a distant observer. Although carrying a relatively small fraction of the total observed flux, the scattered radiation tends to be highly polarized and in a direction perpendicular to the direct radiation. We show how these new features of the polarization spectra may be developed into a powerful tool for measuring black hole spin and probing the gas flow in the innermost disk.
6 pages, 3 figures, proceedings of "The Coming of Age of X-ray Polarimetry," Rome, Italy, April 27-30, 2009