Evolution of a stable BU2 solution. The upper panel shows a comparison between the initial values (solid lines) of equatorial (green) and axial (blue) densities and of equatorial rotational velocity v (magenta), against the value of the same quantities at at t_max = 1500 (dashed lines). The densities are normalized to the central initial value ρ_c, the velocity to its maximum initial value (0.1619). The insert shows the relative difference between the equatorial densities as a function of radius. The spike at r ≈ 8 is due to diffusion at the NS surface, also partly visible in the velocity profile. The middle panel shows the variation in time of the central density. The bottom panel shows the Fourier transform of the the density (green solid line), v^r (red dotted line), v^φ (magenta dashed line), and v^θ (blue dot-dashed line), at the point r = 3.0, θ = 45° of model BU2. The vertical markers indicate the frequency of known eigenmodes. The frequency resolution of our time series is  ~150 Hz.