Comparison of the on-axis afterglow of a GRB 170817A-like jet with an AT2017gfo-like kilonova. Each panel shows light curves in a different band, as indicated in the upper right corner. Solid coloured lines represent the on-axis (θ_v = 0°) jet afterglow (with best-fit parameters and n = 5 × 10⁻³ cm⁻³), with the hatched region showing the portion of the plane span when assuming ISM densities between n = 10⁻⁴ cm⁻³ and n = 1 cm⁻³. Grey solid lines and the grey shaded region show the same information for a jet seen at the core border (θ_v = θ_c). Black dashed lines show the AT2017gfo kilonova best-fitting model from Villar et al. (2017). The orange points show the median kilonova peak magnitudes and peak times in the three bands, as inferred by Ascenzi et al. (2019) and the error bars enclose 68% of the events according to their distributions.