Deciphering signatures of Bardeen black holes from the observed quasi-periodic oscillations

Abstract

Quasi-periodic oscillations (QPOs) observed in the power spectrum of black holes are unique observational probes to the background spacetime since they can be directly related to the timescales associated with the motion of matter orbiting in the vicinity of the black hole horizon. In this regard, the high frequency QPOs (HFQPOs) are particularly interesting as they occur in commensurable pairs, the most common ratio being the 3:2 twin peak QPOs. The theoretical models which aim to explain these QPOs express the observed frequencies in terms of the epicyclic motion of test particles in a given background spacetime. In this work, we study the signatures of Bardeen spacetime from the observed QPOs in the black hole power spectrum. Bardeen black holes are rotating, regular black holes with a magnetic monopole charge. Such regular backgrounds are theoretically interesting as they can potentially evade the curvature singularity, otherwise unavoidable in general relativistic black holes. We perform a χ2 analysis by comparing the available observations of the quasi-periodic oscillations from black hole sources with the relevant theoretical models and note that the Kerr black holes in general relativity are observationally more favored compared to black holes with a monopole charge. Our analysis reveals that black holes with very high monopole charges are disfavored from QPO related observations.

Testing black holes in non-linear electrodynamics from the observed quasi-periodic oscillations

“…The analysis works perfectly fine for regular black holes as well as for black holes with r = 0 curvature singularity as long as the metric is characterized by three parameters, namely, mass, spin and some charge. We have used this method to constrain the tidal charge parameter of braneworld black holes [133] and the magnetic monopole charge parameter of Bardeen black holes where Bardeen black holes are regular black holes with a de Sitter core [134]. This analysis can be further extended to more general regular black holes.…”

Testing alternative spacetimes by high-frequency quasi-periodic oscillations observed in microquasars and active galactic nuclei

“…• Regular Bardeen BHs [71,72], tested for QPOs in [73,74] • Regular Ayón-Beato-Garica (ABG) BHs [69,75] • Regular Hayward BHs [76]…”

Signatures of regular black holes from the shadow of Sgr A* and M87*

“…The observational signatures of regular black holes have been studied quite extensively [49][50][51][52][53][54][55][56][57][58][59][60][61]. In this work we investigate the nature of the black hole shadow cast by the regular black holes discussed above.…”