Origin of neutron stars

Neutron stars are the likely outcome of the electron capture induced collapse of the O-Ne-Mg cores of 8-10 Msub solar stars and the photo-disintegration induced collapse of the Fe-Ni cores of more massive stars. Stars with mass > 100 Msub solar do not leave neutron star remnants. Carbon ignition in the core of a 4-8 Msub solar star is likely to lead to complete disruption, but collapse may be a possibility. The cores of stars with initial less than or equal to 10 Msub solar can become white dwarfs in binary systems. The O-Ne-Mg white dwarfs probably form neutron stars. Observations which bear on these theoretical scenarios are reviewed. 49 references, 2 tables