Kilonova and afterglow lightcurves in the K band for two jet opening angles 0.1 rad (left panel) and 0.2 rad (right panel). Three kilonova models are represented: two red ones (full black lines) assuming a uniform opacity κ = 10 cm² g⁻¹, an expansion velocity v_exp = 0.2c and masses M_KN = 0.01 (lower curve) and 0.1 M_⊙ (upper curve) and a composite model, sum of a red (M_KN = 0.04 M_⊙, v_exp = 0.15c, κ = 10 cm² g⁻¹) and a blue (M_KN = 0.012 M_⊙, v_exp = 0.3c, κ = 0.5 cm² g⁻¹) component (purple, red and blue lines respectively). The dots connected by a dashed line correspond to the light curve of the kilonova associated with GW 170817 transported to a redshift z = 0.3. The three groups of dotted lines are afterglow light curves for an isotropic kinetic energy of 10⁵⁰ (lower), 10⁵¹ (middle) and 10⁵² erg (upper group). In each group the four lines correspond to an increasing density of the external medium from 10⁻³ to 1 cm⁻³. The adopted values of the microphysics parameters are ϵ_e = 0.1 and ϵ_B = 10⁻³.