Note that the Roche model, based on two point masses, represents a very realistic description of equipotentials of real binaries. This is due to the fact that the mass concentration toward the centre is usually very high in real stars. Moreover, the inner equipotential surfaces below the critical Roche lobe are nearly circular and it is known that the outer potential of a mass sphere is identical to that of a mass point. The mass of the outer parts of the stars, violating the spherical symmetry, is negligible with respect to the total mass of the star in all practical applications.

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Hereafter, we will call the rotation of star 1 asynchronous if the absolute values of the vector of axial rotation of star 1 and vector of the orbital revolution are not equal, i.e. $\vert{\vec \Omega}_{\star}\vert \ne \vert {\vec \Omega} \vert$ , but they are parallel to each other: ${\vec \Omega}_{\star} \parallel {\vec \Omega}$ .

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... shown).

Angle $\alpha\in[-\pi,\pi]$ is reckoned counter-clockwise from X axis.

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...R

Note that the present modelling, which describes outflow of matter from a localized area at the equator of a rotating star in a detached binary system, differs principally from our previous modelling of mass exchange in the semidetached binary system $\beta$ Lyr which led to the formation of an accretion disk, halo and jet-like structures perpendicular to the orbital plane - see Bisikalo et al. (1998).

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