  We have tested the appropriateness of two-soliton analytic metric to describe
the exterior of all types of neutron stars, no matter what their equation of
state or rotation rate is. The particular analytic solution of the vaccuum
Einstein equations proved quite adjustable to mimic the metric functions of all
numerically constructed neutron-star models that we used as a testbed. The
neutron-star models covered a wide range of stiffness, with regard to the
equation of state of their interior, and all rotation rates up to the maximum
possible rotation rate allowed for each such star. Apart of the metric
functions themselves, we have compared the radius of the innermost stable
circular orbit $R_{\rm{ISCO}}$, the orbital frequency
$\Omega\equiv\frac{d\phi}{dt}$ of circular geodesics, and their epicyclic
frequencies $\Omega_{\rho}, \Omega_z$, as well as the change of the energy of
circular orbits per logarithmic change of orbital frequency $\Delta\tilde{E}$.
All these quantities, calculated by means of the two-soliton analytic metric,
fitted with good accuracy the corresponding numerical ones as in previous
analogous comparisons (although previous attempts were restricted to neutron
star models with either high or low rotation rates). We believe that this
particular analytic solution could be considered as an analytic faithful
representation of the gravitation field of any rotating neutron star with such
accuracy, that one could explore the interior structure of a neutron star by
using this space-time to interpret observations of astrophysical processes that
take place around it.
