Evolution of the size distribution as a function of time in a set of single-annulus simulations, described in Sect. 5.1, which should be consulted for details. The three panels correspond to environments with the different values of the critical velocity v_c and critical size d_c, previously shown in Fig. 2, at different locations (as labeled) in the disk around the primary star in the γ Cephei system. The vertical dotted lines correspond to the critical size d_c, and the vertical dashed lines correspond to the initial size of the planetesimals d_init.