Reaching resonance. The three columns show three examples of the evolution of stellar orbits under the growing force due to the distortion for different values of the initial frequency: ω = 2.5, 3, and 3.5. The solutions to Equation (2) were obtained with the force parameters F₀ = 10 and α = 0.1 in all cases. The blue lines correspond to the initial oscillations and orbits, while the red lines show the modified ones. The panels of the upper row show the variation of the vertical position of the star along the orbit, while the next rows show the full orbits combining the motion along z with an ellipse in the xy plane without (blue, second row) and with (red, third row) the action of the force and the two combined (lower row).