  We employ an effective gravitational stellar final collapse model which
contains the relevant physics involved in this complex phenomena: spherical
radical infall in the Schwarzschild metric of the homogeneous core of an
advanced star, giant magnetic dipole moment, magnetohydrodynamic material
response and realistic equations of state (EOS). The electromagnetic pulse is
computed both for medium size cores undergoing hydrodynamic bounce and large
size cores undergoing black hole formation. We clearly show that there must
exist two classes of neutron stars, separated by maximum allowable masses:
those that collapsed as solitary stars (dynamical mass limit) and those that
collapsed in binary systems allowing mass accretion (static neutron star mass).
Our results show that the electromagnetic pulse spectrum associated with black
hole formation is a universal signature, independent of the nuclear EOS. Our
results also predict that there must exist black holes whose masses are less
than the static neutron star stability limit.
