Testing regular black holes with X-ray and GW data

TL;DR

This paper tests a model of regular black holes without singularities using X-ray and gravitational wave data, constraining the regularization parameter and finding results consistent with classical black holes.

Contribution

It applies observational data to constrain the regularization parameter of a rotating regular black hole model, bridging theory and astrophysical observations.

Findings

Data are consistent with a vanishing regularization parameter.

Upper bounds on the regularization parameter are l/M < 0.49 from X-ray data.

Upper bounds on the regularization parameter are l/M < 0.72 from GW data.

Abstract

The presence of spacetime singularities in physically relevant solutions of the Einstein Equations is normally interpreted as a symptom of the breakdown of classical general relativity at very high densities/curvatures. However, despite significant efforts in the past decades, we do not have yet any robust theoretical framework to solve the problem of spacetime singularities. In this context, the past few years have seen an increasing interest in the study of phenomenological scenarios to describe singularity-free black holes, gravitational collapses, and cosmological models. In the present work, we consider the recent proposal by Mazza, Franzin & Liberati for a rotating regular black hole and we measure their regularization parameter $l$ from the available X-ray and gravitational wave black hole data. For $l = 0$, we recover the singular Kerr solution of general relativity, while for $l \neq 0$ we can have a regular black hole or a regular wormhole. Our analysis shows that the available data are consistent with a vanishing regularization parameter $l$ and we can constrain its value. From a NuSTAR spectrum of the Galactic black hole in EXO 1846-031, we find $l/M < 0.49$ (90% CL). From the gravitational wave event GW190707A, we find $l/M < 0.72$ (90% CL).