  Outcomes of numerical relativity simulations of massive core collapses or
binary neutron star mergers with moderate masses suggest formations of rapidly
and differentially rotating neutron stars. Subsequent fall back accretion may
also amplify the degree of differential rotations. We propose new formulations
for modeling differential rotations of those compact stars, and present
selected solutions of differentially rotating, stationary, and axisymmetric
compact stars in equilibriums. For the cases when rotating stars reach break-up
velocities, the maximum masses of such rotating models are obtained.
