Notices to investigation of symbiotic binaries. III. Approximation of the Roche lobe parameters for asynchronously rotating star in a binary system

We derive approximative analytical formulas for the basic parameters of the Roche lobe, its radius and the position of the L₁-point, for asynchronously rotating component in a binary system. Our solution is valid in the range of the mass ratio 0.1 < q < 10 and the parameter 1 ≤ p ≤ 20 (p = P_orb/P_rot). Deviations between numerical solution and that given by our analytical approximation are less than 7%.