  We reexamine the gravitational collapse of rotating neutron stars to black
holes by new 3+1 numerical relativity simulations employing the Z4c formulation
of Einstein equations, the moving puncture gauge conditions, and a conservative
mesh refinement scheme for the general relativistic hydrodynamics. The end
state of the collapse is compared to the vacuum spacetime resulting from the
evolution of spinning puncture initial data. Using a local analysis for the
metric fields, we demonstrate that the two spacetimes actually agree.
Gravitational waveforms are analyzed in some detail. We connect the emission of
radiation to the collapse dynamics using simplified spacetime diagrams, and
discuss the similarity of the waveform structure with the one of black hole
perturbation theory.
