Can Rotational Properties of General Relativistic Compact Objects Be Predicted from Static Ones

We propose an approximate description of basic parameters (radius, mass and oblateness) of general relativistic compact rotating objects in terms of the parameters of the static configuration and of the angular velocity only. The representation in terms of static properties is derived using the condition of stationary equilibrium together with some phenomenological assumptions. The predicted radius and mass of rotating neutron star (described by some realistic equations of state) and strange star (described by the bag model equation of state) are compared with data obtained by numerical integration of gravitational field equation. The obtained formulae also allow a simple derivation of the "empirical" equation relating the maximum rotation frequency $\Omega_{max}$ of uniformly rotating star models to the mass and radius of the maximum allowable mass configuration of the non-rotating model.