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.
