Super-spinning compact objects and models of high-frequency quasi-periodic oscillations observed in Galactic microquasars - II. Forced resonances
2017
In our previous work ( Paper I) we applied several models of
high-frequency quasi-periodic oscillations (HF QPOs) to
estimate the spin of the central compact object in three
Galactic microquasars assuming the possibility that the central
compact body is a superspinning object ( or a naked
singularity) with external spacetime described by Kerr geometry
with a dimensionless spin parameter a equal to cJ/GM^(2) > 1.
Here we extend our consideration, and in a consistent way
investigate implications of a set of ten resonance models so
far discussed only in the context of a < 1. The same physical
arguments as in Paper I are applied to these models, i.e. only
a small deviation of the spin estimate from a = 1, a greater
than or similar to 1, is assumed for a favoured model. For five
of these models that involve Keplerian and radial epicyclic
oscillations we find the existence of a unique specific QPO
excitation radius. Consequently, there is a simple behaviour of
dimensionless frequency M x nu_(U)(a) represented by a single
continuous function having solely one maximum close to a
greater than or similar to 1. Only one of these models is
compatible with the expectation of a greater than or similar to
1. The other five models that involve the radial and vertical
epicyclic oscillations imply the existence of multiple resonant
radii. This signifies a more complicated behaviour of M x
nu_(U)(a) that cannot be represented by single functions. Each
of these five models is compatible with the expectation of a
greater than or similar to 1.
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