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Stephen Eikenberry
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Precision Cosmology with Gravitational Waves: GW170817 & the Hubble Parameter
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The LIGO/Virgo detectors observed the merger
of a binary neutron star system in the gravitational
wave event GW170817. The LIGO-Virgo localization
led to the identification of an optical transient
signal with a ~2 kpc projected offset from
the galaxy NGC4993, making GW170817 the first
GW source with a known host galaxy. This
event can thus be used as a "standard siren"
to measure the Hubble parameter, combining
the distance inferred purely from the gravitational
wave signal with the Hubble flow velocity
of the galaxy containing the optical transient.
Such measurements do not require a “distance
ladder”; the gravitational wave analysis
directly estimates the luminosity distance.
I will discuss the measured value of the
Hubble parameter, as well as the potential
for future precision cosmology studies from
gravitational wave observations.

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