Regularized stable Kerr black hole: cosmic censorships, shadow and quasi-normal modes

Abstract

Black hole solutions in general relativity come with pathologies such as singularity and mass inflation instability, which are believed to be cured by a yet-to-be-found quantum theory of gravity. Without such consistent description, one may model theory-agnostic phenomenological black holes that bypass the aforesaid issues. These so-called regular black holes are extensively studied in the literature using parameterized modifications over the black hole solutions of general relativity. However, since there exist several ways to model such black holes, it is important to study the consistency and viability of these solutions from both theoretical and observational perspectives. In this work, we consider a recently proposed model of regularized stable rotating black holes having two extra parameters in addition to the mass and spin of a Kerr solution. We start by computing their quasi-normal modes under scalar perturbation and investigate the impact of those additional parameters on black hole stability. In the second part, we study shadows of the central compact objects in $$M87^*$$ M 87 ∗ and $$Sgr\, A^*$$ S g r A ∗ modelled by these regularized black holes and obtain stringent bounds on the parameter space requiring consistency with Event Horizon Telescope observations.

A connection between regular black holes and horizonless ultracompact stars

“…If these roots have the same value, being therefore a double root, the corresponding horizon is extremal in the sense that the associated surface gravity vanishes. It is also possible to have intermediate situations in which both horizons have distinct positions, but one of them is extremal [31,32,73].…”

Parameter estimation of the Bardeen-Kerr black hole in cloud of strings using shadow analysis

“…These black holes may have survived due to their topological stability and can provide clues about the observables in early universe. They belong to Bardeen type space-time [9] and its generalizations [10][11][12][13][14][15][16][17][18][19][20][21][22].…”

Gravitational lensing by a stable rotating regular black hole

“…When a large number of photons pass nearby, black holes will reveal a dark shadow, the photon ring, and the relativistic images caused by the gravitational lensing effect close to the event horizon. Since the black hole shadow resulting from gravitational lensing effect was proposed, related research has been booming [49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67]. This significant gravitational lensing JCAP05(2024)121 effect can be described under the strong deflection limit.…”

“…Many physical phenomena on the SRR black hole have been explored, such as quasinormal modes and the black hole shadow [67]. In the study of the black hole shadow, the authors explored the shadow structure of the SRR black hole and the impact of the black hole parameters (e, b) on it.…”