Secular evolution over 2 × 10⁷yr of GJ 436b assuming an initial value a = 0.287 AU and a perturber with m′ = 0.1 M_Jup and a′ = 3.583 AU (T′ = 10 yr): eccentricity (top left), semi-major axis (top right), rotation speed with respect to the orbital mean-motion (Ω/n, bottom left), and obliquity angle (bottom right). On the eccentricity plot we overplot in red the result of the same integration, but using a conventional Bulirsh & Stoer integrator.