Standard siren measurement of the Hubble constant using GW170817 and the latest observations of the electromagnetic counterpart afterglow
A. Palmese, Rupinder Kaur, A. Hajela, R. Margutti, A. McDowell, Andrew MacFadyen
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 $\ensuremath{\sim}3.5\text{ }\text{ }\mathrm{years}$ after the GW detection, and properly take into account the impact of the host galaxy peculiar velocity. We find ${75.46}_{\ensuremath{-}5.39}^{+5.34}\text{ }\text{ }\mathrm{km}\text{ }{\mathrm{s}}^{\ensuremath{-}1}\text{ }{\mathrm{Mpc}}^{\ensuremath{-}1}$ (68% credible interval), a $\ensuremath{\sim}7%$ precision measurement, which is a significant improvement compared to the 14% precision of the first standard siren measurement. Our result is consistent within $1\ensuremath{\sigma}$ with the cepheid-anchored supernova and within $1.5\ensuremath{\sigma}$ 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.