Relativistic reflection X-ray spectra of accretion disks

TL;DR

This paper models the relativistic reflection spectra of accretion disks around black holes, highlighting how relativistic effects distort X-ray features and emphasizing the need for accurate models to interpret AGN observations.

Contribution

It provides detailed relativistic calculations of X-ray reflection spectra from accretion disks, accounting for black hole gravity and motion effects, crucial for accurate black hole parameter estimation.

Findings

Spectra are significantly modified by relativistic effects.

Energy shifts and smearing depend on disk parameters.

Proper modeling is essential to avoid spurious features.

Abstract

We have calculated the relativistic reflection component of the X-ray spectra of accretion disks in active galactic nuclei (AGN). Our calculations have shown that the spectra can be significantly modified by the motion of the accretion flow and the gravity and rotation of the central black hole. The absorption edges in the spectra suffer severe energy shifts and smearing, and the degree of distortion depends on the system parameters, in particular, the inner radius of the accretion disk and the disk viewing inclination angles. The effects are significant. Fluorescent X-ray emission lines from the inner accretion disk could be powerful diagnostic of space-time distortion and dynamical relativistic effects near the event horizons of accreting black holes. However, improper treatment of the reflection component in fitting the X-ray continuum could give rise to spurious line-like features. These features mimic the true fluorescent emission lines and may mask their relativistic signatures. Fully relativistic models for reflection continua together with the emission lines are needed in order to extract black-hole parameters from the AGN X-ray spectra.