Hubble constant determination with prior distribution from GW170817. (a) shows the 1 sigma and 2 sigma contours on the parameter space on inclination angle and H₀ with no KN constraint (black) and with KN constraint from MAAT data (red) and broadband gri photometry (blue). (b) shows the EM priors applied to the GW posterior extracted from MAAT data (red) and gri AT 2017gfo observed photometry (blue). (c) The marginalization on H₀ for the GW posterior (black) and the reweighted posterior with MAAT prior (red) and gri prior (blue) applied. This event occurred at a luminosity distance of 40 Mpc, corresponding to a redshift of around 0.009.