Posterior on H₀ obtained by treating SN 2019npv as the electromagnetic counterpart preceding GW190814, shown for the two redshift-prior conventions. The top panel shows the volumetric prior, and the bottom panels shows the flat-in-redshift prior. Each panel shows GW190814 (black, shaded) and GW170817 (blue dashed; B. P. Abbott et al. 2017); their joint posterior (purple) is the product of the two single-event likelihoods under a single H₀ prior, π(H₀) ∝ 1/H₀, and it assumes SN 2019npv is the true host (see Appendix B for the chance-coincidence statistics). Labels give the maximum a posteriori value and minimal 68.3% credible interval; vertical bands mark Planck 2018 (blue) and SH0ES (red).