Observational signatures of rotating black holes in the semiclassical gravity with trace anomaly

TL;DR

This paper investigates the observational signatures of a quantum-corrected rotating black hole solution in semiclassical gravity, focusing on shadow size, photon rings, and accretion disk images to identify potential quantum effects.

Contribution

It provides the first detailed analysis of observational features of a quantum-corrected Kerr black hole, highlighting how trace anomaly influences black hole shadows and photon rings.

Findings

Shadow area varies with the coupling parameter α, being smaller for negative α and larger for positive α.

Prograde and retrograde light rings' radii increase monotonically with α.

High-spin black hole features are highly sensitive to quantum corrections, affecting near-horizon emission.

Abstract

In a recent work by Fernandes [arXiv:2305.10382], an exact stationary and axisymmetric solution was discovered in semiclassical gravity with type-A trace anomaly, identified as a quantum-corrected version of the Kerr black hole. In this study, we explore the observational signatures of this black hole solution. Our investigation reveals that there exist prograde and retrograde light rings, whose radii increase monotonically with the coupling parameter $\alpha$. We also observe that when $\alpha$ is negative, the shadow area for the quantum-corrected black hole is smaller than that of the Kerr black hole, whereas when $\alpha$ is positive, the area is larger. Furthermore, for a near-extremal black hole, its high-spin feature (the NHEKline) is found to be highly susceptible to disruption by $\alpha$. Moreover, we discuss the images of the quantum-corrected black hole in the presence of a thin accretion disk and compare them to those of the Kerr black hole. Our study highlights the importance of near-horizon emission sources in detecting the effects of quantum corrections by black hole images.