On the accretion flow geometry in A0535+26

The geometry of accretion ow in the Be/X-ray transient A0535+26 is explored . It is shown that neither moderate nor giant X-ray flaring events observed in the system can be interpreted within the spherically symmetrical accret ion model and hence the formation of an accretion disk around the neutron s tar magnetosphere during the both types of flares is required. The accretio n disk can be formed at the periastron if (i) the expansion velocity of the Be star envelope in the equatorial plane is V-wr < 150 kms(-1) and (ii) th e parameter accounting for the accretion ow inhomogeneities, <xi>, satisfie s the following condition: xi greater than or similar to 0.16 (M)over dot(1 7)(-1/7) M-17 is the rate of mass capture by the neutron star expressed in units of 10(17) g s(-1). We suggest that the "missing" outburst phenomenon can be associated with the spherically symmetrical accretion onto the inter change-stable magnetosphere of the neutron star. The average spin up rate o f the neutron star during moderate flares less than or similar to3.5 10(-12 ) Hzs(-1) is predicted.