Kinetic energy-external medium density diagrams for short GRBs. The upper (lower) diagrams correspond to M_KN = 10⁻² (10⁻¹) M_⊙ while the left (right) ones correspond to a jet opening angle θ_j = 0.1 (0.2 rad). In each diagram the diagonal line represents events where the jet break takes place at the peak of the kilonova. The three lines that break when they cross this diagonal, limit the regions where the kilonova is brighter than the afterglow (on the left of the line). The full, dashed and dotted lines correspond to three values of : 10, 1 and 0.1. The dots represent GRBs in the sample studied by Fong et al. (2015), in green when a kilonova has been found, in blue (in red) when the measured redshift is below (above) z = 0.4, in black when the redshift is not known. In the first diagram, GRBs closer than z = 0.4 are identified.