A standard siren measurement of the Hubble constant using GW170817 and the latest observations of the electromagnetic counterpart afterglow

Abstract

We present a new constraint on the Hubble constant $H_0$ using the latest measurements of the electromagnetic counterpart to the gravitational wave (GW) event GW170817. We use the latest optical, X-ray and radio observations of the afterglow up to $\sim 3.5$ years after the GW detection, and properly take into account the impact of the host galaxy peculiar velocity. We find $75.46_{-5.39}^{+5.34}$ km s${}^{-1}$ Mpc${}^{-1}$ (68\% Credible Interval), a $\sim 7\%$ precision measurement, which is a significant improvement compared to the $14\%$ precision of the first standard siren measurement. Our result is consistent within $1\ddot{I}ƒ$ with the Cepheid-anchored Supernova and within $1.5\ddot{I}ƒ$ with the Cosmic Microwave Background measurements of the Hubble constant. We also explore the impact of the various assumptions made when fitting for the afterglow on the Hubble constant estimate.

9 pages, 5 figures