1996A&A...314..576B

We investigate the orbital behaviour of close high mass X-ray binaries (HMXBs), including the effects of the evolutionary growth of the moment of inertia and mass loss by stellar wind from the main-sequence star. We find that a nearly synchronous state implies in the context of tidal evolution a rapid decrease of the orbital period for binary systems close to the Darwin instability. In this frame, the observed orbital decays |{dot}(P)/P|≥10^–6yr^–1 in the Cen X-3 and SMC X-1 systems appear to be characteristic of synchronous HMXBs containing a neutron star. The rate of change in orbital period is expected to be one or two orders of magnitude smaller in close HMXBs with black hole candidates.