Testing black hole candidates with electromagnetic radiation

TL;DR

This paper reviews methods to test if astrophysical black hole candidates are described by the Kerr solution of general relativity using electromagnetic radiation observations, discussing current techniques and constraints.

Contribution

It provides a comprehensive overview of current approaches and future prospects for testing the Kerr black hole hypothesis through electromagnetic observations.

Findings

Current observational constraints on Kerr black holes

Potential of future telescopes to test black hole metrics

Summary of methods to analyze electromagnetic radiation around black holes

Abstract

Astrophysical black hole candidates are thought to be the Kerr black holes of general relativity, but there is not yet direct observational evidence that the spacetime geometry around these objects is described by the Kerr solution. The study of the properties of the electromagnetic radiation emitted by gas or stars orbiting these objects can potentially test the Kerr black hole hypothesis. In this paper, I review the state of the art of this research field, describing the possible approaches to test the Kerr metric with current and future observational facilities and discussing current constraints.