a spin-up or spin-down. The large and steady spin-up rates were seen during the giant outbursts. This implies the correlation between torque and observed X-ray flux, which is difficult to explain with direct wind accretion. Assuming observed X-ray luminosity is proportional to the bolometric luminosity, i.e. mass accretion rate, spin-up rate and X-ray flux correlation can be explained by accretion from accretion disk when the net torque is positive and of the order of the material torque [@Gho79; @Gho93]. Thus, it means that transient accretion disks are forming during the giant outbursts [@Kri83] [@Ste86; @Mot91].

When the NS in a Be/NS binary system leaves the dense equatorial disc of the companion, the accretion disk can no longer be fed by the surrounding material. In this case, accretion disc may disappear an the NS may either continue to accrete from the non-equatorial wind of the companion or may enter the propeller phase [@Ill75]. In case accretion is the result of the companion’s non-equatorial wind, it is possible to see erratic spin-up and spin-down episodes [@Bil97; @Ina00]. In case wind of the companion does not cause accretion, propeller phase may set in, when spin pulsation cessation is accompanying by the flux decreasing 