Panel a: effective potential as a function of ρ. Changing the value of parameter ρ_C is equivalent to rescaling the axes. The unit level on the vertical axis gives the intervals of ρ allowed for the particle, such that U(ρ) < 1. These intervals are delimited by ρ₁, ρ₂, and ρ₃, given at (Eq. (22)). Panel b: angular velocity as a function of ρ. Panel c: examples of trajectories for three orbit types, obtained by using the expression from (Eq. (26)) with parameters ρ_C = (1:01; 0:5; 0:9) for (red, green, blue). The axes are rescaled such that ρ_C appears the same, as in panel a.