We study accretion onto the neutron star in Be/X-ray binaries , using a 3D SPH code and the data imported from a high resolution simulation by Okazaki et al .
( 2002 ) for a coplanar system with a short period ( P _ { orb } = 24.3 d ) and moderate eccentricity ( e = 0.34 ) .
We find that a time-dependent accretion disk is formed around the neutron star in Be/X-ray binaries .
The disk shrinks after the periastron passage of the Be star and restores its radius afterwards .
Our simulations show that the truncated Be disk model for Be/X-ray binaries is consistent with the observed X-ray behavior .