Left panel: capture probability to the spin-orbit resonance in a Colombo top model with an adiabatically slow change in the asteroid rotation period P (at the abscissa). Heliocentric orbit of (208) Lacrimosa, dynamical ellipticity Δ = 0.35, and s₆ mode of the orbital node precession were used. With these assumptions, the resonance bifurcates at ≃ 8.73 h rotation period (vertical dashed line). The red line indicates probability P₊ of a capture from orbits originally circulating about the Cassini state C₃, the blue line indicates probability P₋ of a capture from orbits originally circulating about the Cassini state C₁. The analytical theory of Henrard & Murigande (1987) is briefly recalled in the appendix; see Eqs. (A.12) and (A.13). The upper abscissa shows obliquity ε₂ of the Cassini state C₂, the equilibrium point of the resonance. Right panel: phase portrait of the Colombo top for rotation period P = 14.085734 h (other parameters as above). The gray curves are isolines of the integral C(ε, φ) = constant given by Eq. (A.11). The black curve is the separatrix and the black dot shows the location of the Cassini state C₂. The arrows schematically indicate the capture in the resonance from orbits originally circulating about the Cassini state C₁ (blue) and C₃ (red); in a model where only the rotation period P slowly changes, the former occurs for a decrease in P and the latter occurs for an increase in P.