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General Relativity and Quantum Cosmology, gr-qc, Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE
Abstract:
One of the main goals of gravitational-wave astrophysics is to study gravity
in the strong-field regime and constrain deviations from general relativity
(GR). Any such deviation affects not only binary dynamics and
gravitational-wave emission but also the structure and tidal properties of
compact objects. In the case of neutron stars, masses, radii, and tidal
deformabilities can all differ significantly between different theories of
gravity. Currently, the measurement uncertainties in neutron star radii and
tidal deformabilities are quite large. However, much less is known about how
the large uncertainty in the nuclear equation of state (EOS) might affect tests
of GR using binary neutron star mergers. Conversely, using the wrong theory of
gravity might lead to incorrect constraints on the nuclear EOS. Here, we study
this problem within scalar-tensor (ST) theory. We apply the recently derived
$\ell = 2$ tidal Love numbers in this theory to parameter estimation of
GW170817. Correspondingly, we test if physics beyond GR could bias measurements
of the nuclear EOS and neutron star radii. We find that parameter inference for
both the GR and ST cases return consistent component masses and tidal
deformabilities. The radius and the EOS posteriors, however, differ between the
two theories, but neither is excluded by current observational limits. This
indicates that measurements of the nuclear EOS may be biased and that
deviations from GR could go undetected when analyzing current binary neutron
star mergers.
