Relativistic Disc lines

TL;DR

This paper reviews recent evidence that broad iron-K emission lines in X-ray spectra of black hole systems are relativistic disc lines caused by coronal irradiation, emphasizing the importance of general relativistic effects in their interpretation.

Contribution

It summarizes recent observational and theoretical advances confirming the relativistic origin of broad iron lines in accretion disks around spinning black holes.

Findings

NuSTAR spectra confirm relativistic disc lines in AGN and black hole binaries.

General relativistic effects are crucial for explaining the observed line profiles.

High-frequency reverberation spectra support the disc line interpretation.

Abstract

Broad emission lines, particularly broad iron-K lines, are now commonly seen in the X-ray spectra of luminous AGN and Galactic black hole binaries. Sensitive NuSTAR spectra over the energy range of 3-78 keV and high frequency reverberation spectra now confirm that these are relativistic disc lines produced by coronal irradiation of the innermost accretion flow around rapidly spinning black holes. General relativistic effects are essential in explaining the observations. Recent results are briefly reviewed here.