Black hole shadows in fourth-order conformal Weyl gravity

TL;DR

This paper investigates the characteristics of black hole shadows within fourth-order conformal Weyl gravity, finding that observable differences from general relativity are minimal under current parameter constraints, making detection unlikely.

Contribution

It provides the first detailed analysis of black hole shadows in conformal Weyl gravity, comparing them to general relativity and assessing observational prospects.

Findings

Black hole shadow morphology is similar to GR for realistic parameters.

Significant differences only occur with unrealistically large conformal parameters.

Current gravitational tests constrain these parameters, limiting observational differences.

Abstract

We calculate the characteristics of the "black hole shadow" for a rotating, neutral black hole in fourth-order conformal Weyl gravity. It is shown that the morphology is not significantly affected by the underlying framework, except for very large masses. Conformal gravity black hole shadows would also significantly differ from their general relativistic counterparts if the values of the main conformal gravity parameters, $\gamma$ and $\kappa$, were increased by several orders of magnitude. Such increased values for $\gamma$ and $\kappa$ are currently ruled out by gravitational phenomenology. Therefore, it is unlikely that these differences in black hole shadows will be detected in future observations, carried out by the Event Horizon Telescope or other such experiments.