  Neutron stars in high-mass X-ray binaries (HMXBs) generally accrete from the
wind matter of their massive companion stars. Recently Shakura et al. (2012)
suggested a subsonic accretion model for low-luminosity ($<4\times 10^{36}$
ergs$^{-1}$), wind-fed X-ray pulsars. To test the feasibility of this model, we
investigate the spin period distribution of wind-fed X-ray pulsars with a
supergiant companion star, using a population synthesis method. We find that
the modeled distribution of supergiant HMXBs in the spin period - orbital
period diagram is consistent with observations provided that the winds from the
donor stars have relatively low terminal velocities ($\lesssim 1000$
kms$^{-1}$). The measured wind velocities in several supergiant HMXBs seem to
favor this viewpoint. The predicted number ratio of wind-fed X-ray pulsars with
persistent X-ray luminosities higher and lower than $4\times 10^{36}$
ergs$^{-1}$ is about $1:10$.
