1995A&A...299L..41V

Recently it has become clear that there is a group of X-ray pulsars, with pulse periods close to 6 seconds which are distinct from accreting strongly magnetized neutron stars in X-ray binary systems. Here we argue that these objects are the recent products of the evolution of massive stars. They are unlikely to be neutron stars that formed through accretion induced collapse of a white dwarf. We propose that they are single neutron stars accreting from a disk, the recent remnants of the common-envelope evolution of a high-mass X-ray binary.