Topical Collection: Testing the Kerr spacetime with gravitational-wave and electromagnetic observations

TL;DR

This paper reviews current progress in testing whether astrophysical black holes conform to the Kerr solution of Einstein's equations, using various observational methods including gravitational waves and electromagnetic signals.

Contribution

It compiles recent theoretical and experimental advances towards validating the Kerr paradigm across multiple observational platforms.

Findings

Progress in gravitational-wave tests of Kerr black holes

Advances in X-ray and electromagnetic observations

Evidence supporting the Kerr hypothesis

Abstract

One of the Holy Grails of observational astronomy is to confirm the prediction that black holes in the Universe are described by the Kerr solution of Einstein's field equations of general relativity. This Topical Collection provides a status report of theoretical and experimental progress towards confirming the "Kerr paradigm" through X-ray astronomy, gravitational lensing, stellar tidal disruption events, superradiance, and gravitational-wave observations of black hole binary mergers.