Gravitational-Wave Constraints on Neutron-Star Pressure Anisotropy via Universal Relations

Fuente: arXiv
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Auteurs principaux: Guedes, Victor, Ajith, Siddarth, Lau, Shu Yan, Yagi, Kent
Format: Preprint
Publié: 2025
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author Guedes, Victor
Ajith, Siddarth
Lau, Shu Yan
Yagi, Kent
author_facet Guedes, Victor
Ajith, Siddarth
Lau, Shu Yan
Yagi, Kent
contents Neutron stars may exhibit pressure anisotropy arising from various physical mechanisms, such as elasticity, magnetic fields, viscosity, and superfluidity. We compute the tidal deformability and the $f$-mode oscillation frequency of anisotropic neutron stars using a phenomenological quasi-local model characterized by a single dimensionless anisotropy parameter. We find that while the relation between the tidal deformability and the $f$-mode frequency depends on the degree of anisotropy, it remains largely insensitive to variations in the equation of state (the relation between radial pressure and energy density) for a fixed anisotropy parameter, similar to the isotropic case. Leveraging this anisotropy-dependent universal relation within a statistical framework, we place constraints on the anisotropy parameter using both the gravitational wave observation of GW170817 and simulated data for a GW170817-like event observed by a future network of detectors. We find that the anisotropy parameter can be constrained to order unity with current data, and the bounds remain comparable with future detector sensitivities. Importantly, these constraints are only weakly affected by uncertainties in the neutron-star equation of state.
format Preprint
id arxiv_https___arxiv_org_abs_2510_26042
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Gravitational-Wave Constraints on Neutron-Star Pressure Anisotropy via Universal Relations
Guedes, Victor
Ajith, Siddarth
Lau, Shu Yan
Yagi, Kent
High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
Neutron stars may exhibit pressure anisotropy arising from various physical mechanisms, such as elasticity, magnetic fields, viscosity, and superfluidity. We compute the tidal deformability and the $f$-mode oscillation frequency of anisotropic neutron stars using a phenomenological quasi-local model characterized by a single dimensionless anisotropy parameter. We find that while the relation between the tidal deformability and the $f$-mode frequency depends on the degree of anisotropy, it remains largely insensitive to variations in the equation of state (the relation between radial pressure and energy density) for a fixed anisotropy parameter, similar to the isotropic case. Leveraging this anisotropy-dependent universal relation within a statistical framework, we place constraints on the anisotropy parameter using both the gravitational wave observation of GW170817 and simulated data for a GW170817-like event observed by a future network of detectors. We find that the anisotropy parameter can be constrained to order unity with current data, and the bounds remain comparable with future detector sensitivities. Importantly, these constraints are only weakly affected by uncertainties in the neutron-star equation of state.
title Gravitational-Wave Constraints on Neutron-Star Pressure Anisotropy via Universal Relations
topic High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
url https://arxiv.org/abs/2510.26042