Non-axisymmetric Structure of Accretion Disks around the Neutron Star in Be/X-ray Binaries

摘要

A non-axisymmetric structure of accretion disks around the neutron star in Be/X-ray binaries is studied, analyzing the results from 3D SPH simulations performed by [1]. It is found that a ram pressure due to the phase-dependent mass transfer from the Be-star disk excites a one-armed, trailing spiral structure in the accretion disk around the neutron star. The spiral wave has a transient nature; it is excited around the periastron, when the material is transferred from the Be disk, and gradually damped afterwards. We also find that the orbital phase-dependence of the mass-accretion rate is mainly caused by the inward propagation of the spiral wave excited on the accretion disks.