The Polarization of X-rays from Warped Black Hole Accretion Disks

TL;DR

This paper introduces a relativistic ray-tracing code to analyze X-ray polarization from warped black hole accretion disks, revealing how polarization angles can indicate disk misalignment.

Contribution

Developed a general relativistic ray-tracing code to study X-ray polarization from warped accretion disks, incorporating multiple photon reflections and disk warping effects.

Findings

Polarization angle can indicate disk misalignment.

The code models multiple photon reflections.

Potential to infer black hole spin orientation.

Abstract

It is commonly assumed that in black hole accretion disks the angular momenta of the disk and the black hole are aligned. However, for a significant fraction of stellar mass black holes and supermassive black holes, the momenta may not be aligned. In such systems, the interplay of disk viscosity and general relativistic frame dragging can cause the disk to warp or break into two (or more) distinct planes; this is called the Bardeen-Petterson effect. We have developed a general relativistic ray-tracing code to find the energy spectra and polarization of warped accretion disks, accounting for the emission from the disk and for photons reflecting one or multiple times off the warped accretion disk segments. We find that polarization angle can be used to give a lower limit on the misalignment angle when a previous measurement of the jet, which is thought be aligned with the black hole angular momentum, can be spatially resolved.