Stability analysis of the Keplerian fit of the HIP 65407 planetary system. For fixed initial conditions (Table 4), the phase space of the system is explored by varying the semi-major axis a_p and eccentricity e_p of each planet, HIP 65407b and HIP 65407c, respectively. The red zone corresponds to highly unstable orbits, while the dark-blue region can be assumed to be stable on timescales of a billion years (the color scale shows the D values; see Sect. 5.1.4). The contour curves indicate the 1, 2, 3, 5, 10σ confidence intervals from Δχ².