Critical Emission from a High-Spin Black Hole

TL;DR

This paper analytically studies the universal broadening of electromagnetic emissions from the innermost regions of a rapidly spinning black hole's accretion disk, revealing potentially observable critical behavior.

Contribution

It provides an analytical, universal description of emission line broadening near high-spin black holes, independent of disk surface emissivity.

Findings

Broadening is universal and independent of disk emissivity.

Critical behavior in electromagnetic emissions near high-spin black holes.

Potential observability with current or future telescopes.

Abstract

We consider a rapidly spinning black hole surrounded by an equatorial, geometrically thin, slowly accreting disk that is stationary and axisymmetric. We analytically compute the broadening of electromagnetic line emissions from the innermost part of the disk, which resides in the near-horizon region. The result is independent of the disk's surface emissivity and therefore universal. This is an example of critical behavior in astronomy that is potentially observable by current or future telescopes.