  High-energy phenomena in astrophysics involve quite generally a combination
of relativistic motions and strong gravity. The simultaneous solution of
Einstein equations and General Relativistic MHD equations is thus necessary to
model with accuracy such phenomena. The so-called Conformally Flat Condition
(CFC) allows a simplified treatment of Einstein equations, that can be
particularly efficient in those contexts where gravitational wave emission is
negligible, like core-collapse, or the formation/evolution of neutron stars. We
have developed a set of codes to model axisymmetric MHD flows, in General
Relativity, where the solution of Einstein equations is achieved with a
semi-spectral scheme. Here, we will show how this framework is particularly
well suited to investigate neutron star equilibrium models in the presence of
strong magnetic fields and we will present the XNS code, that has been recently
developed and here updated to treat poloidal and mixed configurations.
