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

TL;DR

This study investigates whether Bardeen black holes, which are regular and have a magnetic monopole charge, can be distinguished from Kerr black holes using observed high-frequency quasi-periodic oscillations, finding Kerr models more consistent with data.

Contribution

The paper provides the first observational constraints on Bardeen black holes using QPO data, comparing their signatures with Kerr black holes through chi-square analysis.

Findings

Kerr black holes are more favored by QPO observations.

High monopole charge Bardeen black holes are disfavored.

QPO data can help distinguish different black hole spacetimes.

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 chi-square 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 charge are disfavored from QPO related observations.