Velocity at infinity versus solar impact parameter for all the stars passing during the last 3 Gyr of the simulations. Tiny, grey dots correspond to stars that do not cause enhancements, black dots to enhancement-procucing stars with M _⋆  < 1.2, small black circles to enhancement-producing stars with 1.2 < M _⋆  ≤ 4, and large black circles to enhancement-producing stars with M_⋆ = 9 (B0 stars).