Fig. 4: Posterior probability distributions for the luminosity distance to the kilonova AT2017gfo.

Distance estimates based on the kilonova EPM for the spectra obtained at 1.43 (blue) and 2.42 (orange) days including sphericity corrections propagated from the line-shape fits. The combined constraint is shown as a red histogram. The gravitational wave standard siren distance estimate⁹ is shown as a dashed green line. The standard siren estimate combined with very-long-baseline interferometry (VLBI) radio inclination angle data^31,32 is shown as a solid green line. Cosmological redshift distances are also plotted for H₀ = 67.36 ± 0.54 km s⁻¹ Mpc⁻¹ (ref. ¹⁹) (dotted purple) and H₀ = 73.03 ± 1.04 km s⁻¹ Mpc⁻¹ (ref. ²¹) (dotted blue).