Left panel: posterior distributions of the real and imaginary parts of Y₁ and Y₂ (1σ and 2σ contours). Y₁ has much smaller uncertainties. Right panel: zoom in of left panel with the level curves of integrable approximate Hamiltonian described in Section 4. The black and green contours show circulating and librating domains and the red line is the separatrix. The orange set represents the posterior distribution of Y₁ and blue points show the N-body integration described in Section 4 which confirm the system is in resonance with a small libration amplitude.