and radial frequency of the stellar motion in the plane perpendicular to the major axis. The calculations were done for the period of the last 4Gyr of each simulation. The angular frequency, $\omega$, was computed in each time step as $v_{\mathrm{t}}/r_{yz}$, where $v_{\mathrm{t}}$ is the tangential part of $(v_y^2 + v_z^2)^{1/2}$ and $r_{yz}=(y^2 + z^2)^{1/2}$. We defined the radial frequency, $\kappa$, as $1/T_{\mathrm{avr}}$, where $T_{\mathrm{avr}}$ is the average time period between two subsequent maxima of $r_{yz}$.

The distributions of the stars in the $\omega\kappa$ plane for all four simulations are shown in the left panels of Fig. \[fig:om\]. Only stellar particles with orbits classified as long-axis tubes are included. The right panels show the distribution of the ratio $\kappa/\omega$ for the same particles. Two branches are clearly visible in the plots. For all simulations the branches have a similar slope of $\kappa(\omega)$: around 1.8 for the upper branch and 1.4 for the lower one. Two sub-families are known to exist among the family of long-axis tube orbits in triaxial systems: the inner and outer long-axis tubes. A natural expectation therefore is that the two branches correspond to these two sub-families.

In order to check this interpretation we tried to identify 