Hairy black holes via gravitational decoupling: light rings, absorption and spectral lines

TL;DR

This paper explores how gravitational decoupling creates new light ring structures in hairy black holes, affecting their absorption spectra and revealing potential quasibound states linked to spectral lines and resonances.

Contribution

It introduces a novel analysis of hairy black holes via gravitational decoupling, highlighting the impact on light rings and absorption spectra, including quasibound states and resonances.

Findings

Quasibound states can produce Breit-Wigner-like resonances.

Light ring structures are influenced by gravitational decoupling parameters.

Numerical results agree with established approximations.

Abstract

We investigate the absorption of massless scalar waves by three distinct hairy black hole solutions obtained through the gravitational decoupling method, considering the weak, the strong or the dominant energy conditions. Remarkably, in certain configurations of hairy black holes associated with the fulfillment of the weak energy condition, quasibound states may appear, resulting in Breit-Wigner-like resonances in their absorption profile. These quasibound states (and consequently the spectral lines in the absorption spectrum) can be related to stable light rings in the spacetime, a structure often associated with horizonless exotic compact objects, such as wormholes. We investigate how the gravitational decoupling method introduces novel light ring structures in hairy black holes and influences the absorption spectra through its deformation parameters. Our numerical results show excellent agreement with well-known approximations.