Posterior joint and marginalised distributions of the free model parameters, E_0, iso^c, θ_c, θ_v, n_ext, ϵ_B, ϵ_e, ζ, pa, Γ₀^c, b for the three fits of the afterglow of GW 170817 presented in Sect. 4, which differ only by the treatment of the radiative processes. In blue, no SSC scatterings are taken into account ("no SSC"); in green, SSC scatterings are assumed to be only in the Thomson regime ("SSC (Thomson)"); in orange, the SSC scattering is depleted at high energy in the KN regime ("SSC (with KN)"). The coloured contours correspond to the 3σ confidence intervals for each model and each parameter.