Hubble constant measurement with 13 bright standard sirens from binary black hole mergers inside active galactic nuclei

We measure the Hubble constant $H_0$ using 13 gravitational-wave binary black hole mergers associated with active galactic nucleus hosts. We find $H_0=70.50_{-2.89}^{+3.37}(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 1.56(\mathrm{c}\mathrm{a}\mathrm{l})$,km,s${}^{-1}$,Mpc${}^{-1}$ ($4.4\mathrm{\%}$ precision), consistent with both Planck,2018 ($0.98\sigma$) and SH0ES,2024 ($0.76\sigma$), with no significant preference between the two. Combining with the bright siren GW170817 sharpens the constraint to $H_0=70.31_{-2.85}^{+3.00}(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 1.55(\mathrm{c}\mathrm{a}\mathrm{l})$,km,s${}^{-1}$,Mpc${}^{-1}$ ($4.2\mathrm{\%}$ precision), and further combining with an independent dark-and-bright-siren sample tightens it to $H_0=69.71_{-2.40}^{+2.55}(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 1.54(\mathrm{c}\mathrm{a}\mathrm{l})$,km,s${}^{-1}$,Mpc${}^{-1}$ ($3.5\mathrm{\%}$ precision). Assuming a luminosity-distance prior centered around the value related to a fixed cosmology in turn, recovers $H_0=67.62\pm 0.72$ (Planck-anchored) and $H_0=72.91\pm 0.72$,km,s${}^{-1}$,Mpc${}^{-1}$ (SH0ES-anchored). We show that under such an assumption, a rejection of $\gtrsim 4\sigma$ to the opposing anchor is obtained.