Self-Consistency and Continuity Questions on Axisymmetric, Rigidly Rotating Polytropes

Axisymmetric, rigidly rotating polytropes are considered in the framework of both the original Chandrasekhar (C33) approximation and a different version (extended C33 approximation). Special effort is devoted to two specific points, namely (i) a contradiction between the binomial series evaluation and the vanishing density on the boundary, which affects the self-consistency of the above mentioned approximations, and (ii) the continuity of selected parameters as a function of the polytropic index, n. Concerning (i), it is shown Emden-Chandrasekhar (EC) associated functions are defined at any internal point even if related EC associated equations hold only for a particular subvolume, in the framework of the extended C33 and the C33 approximation, respectively. Concerning (ii), the continuity may safely be established in the limit, n=0, n=5, for part of the parameters, while additional data are needed for the remaining part. Simple fitting curves, valid to a good extent for a wide range of n, involve exponential functions and, in a single case, two straight lines joined by a parabolic segment. The expression of physical parameters in terms of the polytropic index can be used in building up sequences of configurations with changing density profile for assigned mass and angular momentum.