A Precise Distance to the Host Galaxy of the Binary Neutron Star Merger
  GW170817 Using Surface Brightness Fluctuations
  The joint detection of gravitational waves and electromagnetic radiation from
the binary neutron star (BNS) merger GW170817 has provided unprecedented
insight into a wide range of physical processes: heavy element synthesis via
the $r$-process; the production of relativistic ejecta; the equation of state
of neutron stars and the nature of the merger remnant; the binary coalescence
timescale; and a measurement of the Hubble constant via the "standard siren"
technique. In detail, all of these results depend on the distance to the host
galaxy of the merger event, NGC4993. In this paper we measure the surface
brightness fluctuation (SBF) distance to NGC4993 in the F110W and F160W
passbands of the Wide Field Camera 3 Infrared Channel on the Hubble Space
Telescope (HST). For the preferred F110W passband we derive a distance modulus
of $m{-}M=33.05\pm0.08\pm0.10$ mag, or a linear distance $d=40.7\pm1.4\pm1.9$
Mpc (random and systematic errors, respectively); a virtually identical result
is obtained from the F160W data. This is the most precise distance to NGC4993
available to date. Combining our distance measurement with the corrected
recession velocity of NGC4993 implies a Hubble constant $H_0=71.9\pm
7.1~km~s^{-1}~Mpc^{-1}$. A comparison of our result to the GW-inferred value of
$H_0$ indicates a binary orbital inclination of $i\,{\gtrsim}\,137~\deg$. The
SBF technique can be applied to early-type host galaxies of BNS mergers to
${\sim\,}100$ Mpc with HST and possibly as far as ${\sim\,}300$ Mpc with the
James Webb Space Telescope, thereby helping to break the inherent
distance-inclination degeneracy of the GW signals at distances where many
future BNS mergers are likely to be detected.
