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+3.37-2.89,(stat) plus or minus1.56,(cal),km,s-1,Mpc-1 (4.4% 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+3.00-2.85,(stat) plus or minus1.55,(cal),km,s-1,Mpc-1 (4.2% precision), and further combining with an independent dark-and-bright-siren sample tightens it to H 0=69.71+2.55-2.40,(stat) plus or minus1.54,(cal),km,s-1,Mpc-1 (3.5% precision). Assuming a luminosity-distance prior centered around the value related to a fixed cosmology in turn, recovers H 0=67.62 plus or minus0.72 (Planck-anchored) and H 0=72.91 plus or minus0.72,km,s-1,Mpc-1 (SH0ES-anchored). We show that under such an assumption, a rejection of 4 sigma to the opposing anchor is obtained.