Note on a new parametrization for testing the Kerr metric

TL;DR

This paper introduces a novel parametrization method for testing if astrophysical black holes conform to the Kerr metric by examining the spacetime curvature, exemplified through black hole shadow observations.

Contribution

It presents a new parametrization approach focusing on the curvature strength rather than metric deviations for testing Kerr black holes.

Findings

Proposes a new parametrization for Kerr tests.

Applies the method to black hole shadow observations.

Provides a framework for future observational tests.

Abstract

We propose a new parametrization for testing the Kerr nature of astrophysical black hole candidates. The common approaches focus on the attempt to constrain possible deviations from the Kerr solution described by new terms in the metric. Here we adopt a different perspective. The mass and the spin of a black hole make the spacetime curved and we want to check whether they do it with the strength predicted by general relativity. As an example, we apply our parametrization to the black hole shadow, an observation that may be possible in a not too distant future.