Approximate Universal Relations for Neutron Stars and Quark Stars

By Kent Yagi, N. Yunes. 2016

340 citations recorded by the source corpus.

Abstract Neutron stars and quark stars are ideal laboratories to study fundamental physics at supra nuclear densities and strong gravitational fields. Astrophysical observables, however, depend strongly on the star’s internal structure, which is currently unknown due to uncertainties in the equation of state. Universal relations, however, exist among certain stellar observables that do not depend sensitively on the star’s internal structure. One such set of relations is between the star’s moment of inertia ( I ), its tidal Love number (Love) and its quadrupole moment ( Q ), the so-called I–Love–Q relations. Similar relations hold among the star’s multipole moments, which resemble the well-known black hole no-hair theorems. Universal relations break degeneracies among astrophysical observables, leading to a variety of applications: (i) X-ray measurements of the nuclear matter equation of state, (ii) gravitational wave measurements of the intrinsic spin of inspiraling compact objects, and (iii) gravitational and astrophysical tests of General Relativity that are independent of the equation of state. We here review how the universal relations come about and all the applications that have been devised to date.

Subfields: Astronomy and Astrophysics, Ocean Engineering

View Paper: https://www.semanticscholar.org/paper/5c8a681c5d82b5d8ec2666a53ae935efccd42bcc

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Citations in the corpus

GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo during the First and Second Observing Runs (2018, methodology): “The EOS dependence of each NS’s spin-induced quadrupole moment is included by relating it to the tidal parameter of each NS using the quasi-universal relations of [235].”
Using Gravitational-wave Observations and Quasi-universal Relations to Constrain the Maximum Mass of Neutron Stars (2017, result): “The existence of such a universal relation has been confirmed by several other authors and shown to apply also for other theories of gravity, see e.g., Staykov et al. (2016); Minamitsuji & Silva (2016); Yagi & Yunes (2017).”
Stellar structure models in modified theories of gravity: Lessons and challenges (2019, background): “In the context of general scalar-tensor theories, a complete toolkit for the modelling of X-ray pulse profiles of rotating neutron stars has been recently released by Silva and Yunes [98].”
GWTC-2: Compact Binary Coalescences Observed by LIGO and Virgo During the First Half of the Third Observing Run (2020, methodology): “For the BNS system GW190425 [32], we use the following: IMRPhenomD_NRTidal and IMRPhenomPv2_NRTidal [213,214], which are based on the BBH models IMRPhenomD and IMRPhenomPv2, respectively, and incorporate NR and tidal EOB-tuned contributions from tidal interaction as well as equation-of-state-depende”
Tidal Deformability from GW170817 as a Direct Probe of the Neutron Star Radius (2018, background): “In particular, Yagi & Yunes (2017) found that the relationship can be written as C = a0 + a1 ln Λ + a2(ln Λ) 2, (5) where C ≡ GM/Rc2 is the compactness and the coefficients were fit to be a0 = 0.360, a1 = −0.0355, and a2 = 0.000705.”
GWTC-2.1: Deep extended catalog of compact binary coalescences observed by LIGO and Virgo during the first half of the third observing run (2021, positive): “In addition to the quadrupole tidal effects, other matter effects are parametrized in terms of Λ 1 ; 2 using equation of state (EOS)-insensitive relations [152].”