2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/8690The non-axisymmetric structure of accretion disks around the neutron star in Be/X-ray binaries is studied by analyzing the results from three dimensional (3D) Smoothed Particle Hydrodynamics (SPH) simulations. It is found that 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 is gradually damped afterwards. It is also found that the orbital phase-dependence of the mass-accretion rate is mainly caused by the inward propagation of the spiral wave excited in the accretion disk.4pages, 6figures, Conference Proceeding for the "Interacting Binaries: Accretion, Evolution and Outcome" worshop held in Cefalu' (Italy) in July 2004Astrophysicstext