Stability analysis of the AU Mic planetary system, around the best fit solution (Table 4), with M_c = 25.0 M_⊕ (a), and M_c = 2.2 M_⊕ (b). The phase space of the system is explored by varying the semi-major axis a_c (and thus the period P_c) and eccentricity e_c of the outer planet; e_c is plotted as a function of P_c and not a_c, as the uncertainty on a_c is larger. For the initial conditions, the step size is 0.01 in eccentricity, and 2 × 10⁻⁵ au in semi-major axis. For each initial condition, the system is integrated over 5 kyr and a stability criterion is derived with the frequency analysis of the mean longitude. The chaotic diffusion is measured by the variation in the mean motion. The color scale corresponds to the decimal logarithm of the variation of the mean motion (Correia et al. 2010). The “red” zone corresponds to highly unstable orbits, while the “dark-blue” region canbe assumed to be stable on a billion-years timescale. The main resonances in the vicinity of the solution (13:6, 11:5, 9:4, 7:3) are labeled. It should be noted that for the lower value of the mass M_c (b), the libration island is mostly stable while it is not the case for the larger value of M_c (a).