A Low-mass Primary for Cygnus X-1?

Abstract
If the primary of HDE 226868 (Cyg X-1) is a low mass (0.3–0.5 M ), low surface gravity B star of the type of which the primary of HZ 22 is the prototype, then the secondary falls well within the mass range of stable neutron stars (and white dwarfs), and need not be a black hole.