Delineating effects of nuclear symmetry energy on the radii and tidal polarizabilities of neutron stars

Zhang, Naibo; Li, Bao-An

doi:10.1088/1361-6471/aaef54

Cited by 66 publications

(62 citation statements)

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“…Finally, astronomical observations and terrestrial experiments can be translated to microscopic constraints through the symmetry energy [265], the energy budget for increasing asymmetry between neutrons and protons. Various studies have empirically identified correlations between various combinations of parameters that characterize the symmetry energy and its density dependence with the neutron star radius and tidal parameters [246,[266][267][268][269] or terrestrial experimental results [239,[270][271][272], as they all are linked to the low-density behavior of the equation of state around (twice) saturation. The tidal constraints from GW170817, and more recently radius constraints from NICER have been used to examine implications for the symmetry energy [273][274][275][276][277][278][279][280][281][282] as well as potential systematics in the mapping [283].…”

Section: Microscopic Propertiesmentioning

confidence: 99%

Neutron-star tidal deformability and equation-of-state constraints

2020

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Despite their long history and astrophysical importance, some of the key properties of neutron stars are still uncertain. The extreme conditions encountered in their interiors, involving matter of uncertain composition at extreme density and isospin asymmetry, uniquely determine the stars' macroscopic properties within General Relativity. Astrophysical constraints on those macroscopic properties, such as neutron star masses and radii, have long been used to understand the microscopic properties of the matter that forms them. In this article we discuss another astrophysically observable macroscopic property of neutron stars that can be used to study their interiors: their tidal deformation. Neutron stars, much like any other extended object with structure, are tidally deformed when under the influence of an external tidal field. In the context of coalescences of neutron stars observed through their gravitational wave emission, this deformation, quantified through a parameter termed the tidal deformability, can be measured. We discuss the role of the tidal deformability in observations of coalescing neutron stars with gravitational waves and how it can be used to probe the internal structure of Nature's most compact matter objects. Perhaps inevitably, a large portion of the discussion will be dictated by GW170817, the most informative confirmed detection of a binary neutron star coalescence with gravitational waves as of the time of writing.

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Section: Microscopic Propertiesmentioning

confidence: 99%

Neutron-star tidal deformability and equation-of-state constraints

2020

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“…Given an NS observable, one can find all points (EOSs) necessary to reproduce the observable, thus numerically solving the NS inverse-structure problem. Such an approach has been found very successful in several applications [95][96][97]102].…”

Section: Directly Solving Neutron Star Inverse-structure Problems In the High-density Eos Parameter Spacementioning

confidence: 99%

“…The constant surfaces of radius (left) and tidal polarizability (right) in the symmetry energy parameter space of L − K sym − J sym , respectively. Taken from [102].…”

Section: Directly Solving Neutron Star Inverse-structure Problems In the High-density Eos Parameter Spacementioning

confidence: 99%

Progress in Constraining Nuclear Symmetry Energy Using Neutron Star Observables Since GW170817

Cai²,

Wang

et al. 2021

Universe

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The density dependence of nuclear symmetry energy is among the most uncertain parts of the Equation of State (EOS) of dense neutron-rich nuclear matter. It is currently poorly known especially at suprasaturation densities partially because of our poor knowledge about isovector nuclear interactions at short distances. Because of its broad impacts on many interesting issues, pinning down the density dependence of nuclear symmetry energy has been a longstanding and shared goal of both astrophysics and nuclear physics. New observational data of neutron stars including their masses, radii, and tidal deformations since GW170817 have helped improve our knowledge about nuclear symmetry energy, especially at high densities. Based on various model analyses of these new data by many people in the nuclear astrophysics community, while our brief review might be incomplete and biased unintentionally, we learned in particular the following: (1) The slope parameter L of nuclear symmetry energy at saturation density ρ0 of nuclear matter from 24 new analyses of neutron star observables was about L≈57.7±19 MeV at a 68% confidence level, consistent with its fiducial value from surveys of over 50 earlier analyses of both terrestrial and astrophysical data within error bars. (2) The curvature Ksym of nuclear symmetry energy at ρ0 from 16 new analyses of neutron star observables was about Ksym≈−107±88 MeV at a 68% confidence level, in very good agreement with the systematics of earlier analyses. (3) The magnitude of nuclear symmetry energy at 2ρ0, i.e., Esym(2ρ0)≈51±13 MeV at a 68% confidence level, was extracted from nine new analyses of neutron star observables, consistent with the results from earlier analyses of heavy-ion reactions and the latest predictions of the state-of-the-art nuclear many-body theories. (4) While the available data from canonical neutron stars did not provide tight constraints on nuclear symmetry energy at densities above about 2ρ0, the lower radius boundary R2.01=12.2 km from NICER’s very recent observation of PSR J0740+6620 of mass 2.08±0.07M⊙ and radius R=12.2–16.3 km at a 68% confidence level set a tight lower limit for nuclear symmetry energy at densities above 2ρ0. (5) Bayesian inferences of nuclear symmetry energy using models encapsulating a first-order hadron–quark phase transition from observables of canonical neutron stars indicated that the phase transition shifted appreciably both L and Ksym to higher values, but with larger uncertainties compared to analyses assuming no such phase transition. (6) The high-density behavior of nuclear symmetry energy significantly affected the minimum frequency necessary to rotationally support GW190814’s secondary component of mass (2.50–2.67) M⊙ as the fastest and most massive pulsar discovered so far. Overall, thanks to the hard work of many people in the astrophysics and nuclear physics community, new data of neutron star observations since the discovery of GW170817 have significantly enriched our knowledge about the symmetry energy of dense neutron-rich nuclear matter.

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“…[267]. Some of us have recently made significant efforts in the latter approach [54,241,268]. By using an explicitly isospin-dependent parameterization of the EOS determined by the Eq.…”

Section: Solving the Inverse-structure Problem Of Neutron Stars In A mentioning

confidence: 99%

“…On the other hand, it has already been pointed out in the literature and discussed in detail in Sect. 5.3.1 that translating Λ measurements directly into R constraints has to be taken with caution [387], and that both Λ and R must be measured independently [120,268] to extract meaningful constraints on the EOS of dense neutron-rich matter. Thus, theoretical predictions of the neutron-star moment of inertia are very timely and important in the ongoing efforts to determine the exact details of the EOS.…”

Section: Symmetry Energy Effects On the Moment Of Inertia Of Slowly Rmentioning

confidence: 99%

Towards understanding astrophysical effects of nuclear symmetry energy

et al. 2019

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Determining the Equation of State (EOS) of dense neutron-rich nuclear matter is a shared goal of both nuclear physics and astrophysics. Except possible phase transitions, the density dependence of nuclear symmetry Esym(ρ) is the most uncertain part of the EOS of neutron-rich nucleonic matter especially at supra-saturation densities. Much progresses have been made in recent years in predicting the symmetry energy and understanding why it is still very uncertain using various microscopic nuclear many-body theories and phenomenological models. Simultaneously, significant progresses have also been made in probing the symmetry energy in both terrestrial nuclear laboratories and astrophysical observatories. In light of the GW170817 event as well as ongoing or planned nuclear experiments and astrophysical observations probing the EOS of dense neutron-rich matter, we review recent progresses and identify new challenges to the best knowledge we have on several selected topics critical for understanding astrophysical effects of the nuclear symmetry energy.PACS. 2 6.60.Kp Contents B.A Li, P.G. Krastev, D.H. Wen and N.B. Zhang: Astrophysical Effects of Nuclear Symmetry Energy 5.2.2 Predicted correlation strength between the radii of neutron stars and the symmetry energy from low to high densities 32 5.2.3 Predicted effects of the symmetry energy on the tidal deformability of neutron stars 33 5.3 Post-GW170817 analyses of tidal deformability and radii of neutron stars as well as constraints on the nuclear EOS and symmetry energy . . . 34 5.3.

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Delineating effects of nuclear symmetry energy on the radii and tidal polarizabilities of neutron stars

Cited by 66 publications

References 60 publications

Neutron-star tidal deformability and equation-of-state constraints

Neutron-star tidal deformability and equation-of-state constraints

Progress in Constraining Nuclear Symmetry Energy Using Neutron Star Observables Since GW170817

Towards understanding astrophysical effects of nuclear symmetry energy

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