Posterior distribution of the afterglow spectrum around its peak (t_obs = 110 days) for the “SSC (with KN)” fit of the afterglow of GW 170817. The data points show the multi-wavelength observations at t_obs ± 4 days. The upper limit from H.E.S.S. is also indicated (Abdalla et al. 2020). The low-energy component (solid line) is produced by synchrotron radiation, while the high-energy emission (dashed line) is powered by SSC scattering. The thick lines represent the median value at each observing frequency, the dark contours show the 68% confidence interval, and the light contours present the 97.5% confidence interval. Some instrument observing spectral ranges are shown in colours.