Updated Corbet diagram (1986) showing the different populations of HMXBs (X-ray pulsars) with measured values of both P_orb and P_spin. BeHMXB show a correlation between P_orb and P_spin due to net transfer of angular momentum between the decretion disk of the Be companion star and the neutron star. Beginning atmospheric Roche-lobe overflow (RLO) systems have shorter (likely circularized) orbital periods. Supergiant fast X-ray transients (SFXT) are accreting pulsars exhibiting short and intense flares, spanning nearly the whole range of parameters of this diagram. Finally, supergiant HMXBs are accreting pulsars with quite short orbital periods (most being circularized) and slowly rotating neutron stars. IGR J16320–4751, labeled in this diagram, is one of these persistently accreting systems.