  Kilohertz QPOs can be used as a probe of the inner regions of accretion disks
in compact stars and hence also of the properties of the central object. Most
models of kHz QPOs involve epicyclic frequencies to explain their origin. We
compute the epicyclic frequencies of nearly circular orbits around rotating
strange quark stars. The MIT bag model is used to model the equation of state
of quark matter and the uniformly rotating stellar configurations are computed
in full general relativity. The vertical epicyclic frequency and the related
nodal precession rate of inclined orbits are very sensitive to the oblateness
of the rotating star. For slowly rotating stellar models of moderate and high
mass strange stars, the sense of the nodal precession changes at a certain
rotation rate. At lower stellar rotation rates the orbital nodal precession is
prograde, as it is in the Kerr metric, while at higher rotation rates the
precession is retrograde, as it is for Maclaurin spheroids. Thus,
qualitatively, the orbits around rapidly rotating strange quark stars are
affected more strongly by the effects of stellar oblateness than by the effects
of general relativity. We show that epicyclic and orbital frequencies
calculated numerically for small mass strange stars are in very good agreement
with analytical formulae for Maclaurin spheroids.
