2017A&A...607A..69K

In our previous work (Paper I, 2014A&A...572A..79K ) 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 super-spinning object (or a naked singularity) with external spacetime described by Kerr geometry with a dimensionless spin parameter a∼cJ/GM²>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≥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 Mxν_U(a) represented by a single continuous function having solely one maximum close to a≥1. Only one of these models is compatible with the expectation of a≥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 Mxν_U(a) that cannot be represented by single functions. Each of these five models is compatible with the expectation of a≥1.