Analytical predictions of two-planet systems undergoing convergent migration near the 2:1 MMR in the limits of q≪1 (left) and q≫1 (right). Blue region: planets directly bypass the MMR due to strong eccentricity damping. Brown region: Convergent migration is too fast to allow resonance capture. Green region: planets get trapped in a stable resonance. Yellow region: Despite overstability occurs, planets still get trapped in the resonance, with libration of finite amplitude around the equilibrium point. Purple region: after a temporary trap, planets eventually escape resonance and continue the inward migration. The illustrative examples of the above regimes can be found in Figures 1–5.