primary wind acceleration into account. We describe it as a $\beta$-profile $$v_1(r_1)=v_s+(v_{\rm 1,\infty}-v_s)\left(1-\frac{R_1}{r_1}\right)^{\beta} ,
\label{eq:v1}$$ with a parameter $\beta=1$, where $v_s=20 \km \s^{-1}$ is the sound velocity on the primary surface, $v_{\rm 1,\infty}=500 \km \s^{-1}$ is the primary wind terminal velocity (which was already defined earlier), $r_1$ is the distance from the primary center, and $R_1 = 180 \AU$ is the primary radius. The acceleration of the primary wind becomes important close to periastron, when the binary separation becomes only slightly larger than the primary radius. Being slower and denser close to the surface, the accelerating primary wind yields a denser post shocked primary wind, and affects other variables in this already complex geometry. Its slower velocity makes the hyperboloid asymptotic opening angle wider, and its rotation more pronounced, as we now explain.

\(2) **Hyperboloid asymptotic opening angel.** The radial (along the line joining the two stars) component of the relative velocity between the secondary star and the primary wind is $v_1-v_r$, where $v_r$ the radial component of the orbital velocity; $v_r$ is negative when the two stars approach each other. The relative speed between the secondary and the primary wind is $$v_{\rm wind1} = \left[v_\theta^2 + (v_1-v_r)^2 \right]^{1/2},
\label{eq:vwind1}$$ 