Can Neutron Star Tidal Effects Obscure Deviations from General Relativity?

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Main Authors: Brown, Stephanie M., Krishnan, Badri, Somasundaram, Rahul, Tews, Ingo
Format: Preprint
Published: 2024
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author Brown, Stephanie M.
Krishnan, Badri
Somasundaram, Rahul
Tews, Ingo
author_facet Brown, Stephanie M.
Krishnan, Badri
Somasundaram, Rahul
Tews, Ingo
contents 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.
format Preprint
id arxiv_https___arxiv_org_abs_2411_19129
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Can Neutron Star Tidal Effects Obscure Deviations from General Relativity?
Brown, Stephanie M.
Krishnan, Badri
Somasundaram, Rahul
Tews, Ingo
General Relativity and Quantum Cosmology
High Energy Astrophysical Phenomena
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.
title Can Neutron Star Tidal Effects Obscure Deviations from General Relativity?
topic General Relativity and Quantum Cosmology
High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2411.19129