The X-ray outbursts of Be/X-ray transients
  We present a new scenario for the behaviour of Be/X-ray binaries based on long-term multiwavelength monitoring and the decretion disc model. The circumstellar discs of the primaries are truncated because of the tidal and resonant effect of the neutron star. The geometry of the systems and the value of viscosity determine the presence or absence of Type I X-ray outbursts. The interaction of a strongly disturbed disc with the neutron star originates Type II X-ray and optical outbursts. 
Ignacio Negueruela (SAX SDC, now Strasbourg), Atsuo T. Okazaki   (Hokkai-Gakuen)