the outer (emitting) disk radius $R_{\rm d}$ (Smak 1981): $$\Delta v = 2 R_{\rm d}\Omega_{\rm K} \sin i = 2 \sin i (GM_1/R_{\rm
d})^{1/2},
\label{eq:vrout}$$ where $M_1$ is the mass of the primary and $i$ the system inclination. We can also express $R_{\rm d}/a$ as a function of the velocity semi-amplitude of the secondary $K_2$ and the mass ratio $q=M_2/M_1$ by combining the above equation with the mass function (see below, Eq. \[eq:fm\]) and Kepler’s third law[^2], resulting in: $$\frac{R_{\rm d}}{a}=(1+q)\left(\frac{2 K_2}{\Delta v}\right)^2
\label{eq:rova}$$ The disk outer radius is expected to reach the tidal truncation radius for $q\gsim0.2$ and to be limited to $R_{\rm d}/a\approx0.48$ by the 3:1 resonance for $q\lsim 0.2$ (e.g. Warner 1995). Papaloizou & Pringle (1977; their Tab. 1) give a theoretical estimate of the outer disk radius that we recklessly use for $R_{\rm d}/a$. Eq. \[eq:rova\] can therefore be used to give the semi-amplitudes $K_2(q)$ for which the disk radius is consistent with the theoretical expectations. For $0.01<q<1$ the disk radius varies between 0.5 and 0.3 in units of the binary separation $a$. The expected $K_2$ as a function of $q$ is shown as a solid line in the left panel of Fig. \[fig:cons1\]. We find 