The luminosity distance measurement of GW170817 derived from GW analysis in Abbott et al. 2017 (here, A17:H0) is highly correlated with the measured inclination of the NS-NS system. To improve the precision of the distance measurement, we attempt to constrain the inclination by modeling the broad-band X-ray-to-radio emission from GW170817, which is dominated by the interaction of the jet with the environment. We update our previous analysis and we consider the radio and X-ray data obtained at $t<40$ days since merger. We find that the afterglow emission from GW170817 is consistent with an off-axis relativistic jet with energy $10^{48},rm{erg}<E_{k}le 3times 10^{50} ,rm{erg}$ propagating into an environment with density $nsim10^{-2}-10^{-4} ,rm{cm^{-3}}$, with preference for wider jets (opening angle $theta_j=15$ deg). For these jets, our modeling indicates an off-axis angle $theta_{rm obs}sim25-50$ deg. We combine our constraints on $theta_{rm obs}$ with the joint distance-inclination constraint from LIGO. Using the same $sim 170$ km/sec peculiar velocity uncertainty assumed in A17:H0 but with an inclination constraint from the afterglow data, we get a value of $H_0=$$74.0 pm frac{11.5}{7.5}$ $mbox{km/s/Mpc}$, which is higher than the value of $H_0=$$70.0 pm frac{12.0}{8.0}$ $mbox{km/s/Mpc}$ found in A17:H0. Further, using a more realistic peculiar velocity uncertainty of 250 km/sec derived from previous work, we find $H_0=$$75.5 pm frac{11.6}{9.6}$ km/s/Mpc for H0 from this system. We note that this is in modestly better agreement with the local distance ladder than the Planck CMB, though a significant such discrimination will require $sim 50$ such events. Future measurements at $t>100$ days of the X-ray and radio emission will lead to tighter constraints.
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