Compactness of Neutron Stars

Chen, Wei-Chia; Piekarewicz, J.

doi:10.1103/physrevlett.115.161101

Cited by 72 publications

(169 citation statements)

References 30 publications

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“…Both hadronic and hybrid star radii of 1.4 M are above 12.8 km, within the observations of the objects BNS 4U 1608−522 [61], BNS SAX J1748.9−2021 [62,63], and RP-MSP PSR J0437−4715 [64,65], but out of the range 10.1-11.1 km obtained in [66], from the analysis of spectroscopic radius measurements of twelve neutron stars obtained during thermonuclear bursts or in quiescence. However, in [67], it was shown that in order to prevent the EOS from violating causality, the radius should satisfy R 1.4 10.7 km, if it is imposed that the EOS also describes a 2 M star. In [45], taking experimental constraints and causality restrictions for large maximum masses, the 1.4 M star radii were constrained to be within the interval 12.1 ± 1.1 km (see [68]).…”

Section: Discussionmentioning

confidence: 99%

Neutron stars: From the inner crust to the core with the (extended) Nambu–Jona-Lasinio model

2016

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Nucleonic matter is described within an SU(2) extended Nambu-Jona-Lasinio (NJL) model. Several parametrizations with different nuclear matter saturation properties are proposed. At subsaturation, nuclear pasta phases are calculated within two methods: the coexistence-phases approximation and the compressible liquid drop model, with the surface tension coefficient determined using a geometrical approach at zero temperature. A unified equation of state of stellar matter for the inner crust, with the nuclear pasta phases, and the core is calculated. The mass and radius of neutron stars within this framework are obtained for several families of hadronic and hybrid stars. The quark phase of hybrid stars is described within the SU(3) NJL model including a vector term. Stellar macroscopic properties are in accordance with some of the recent results in the literature.

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Section: Discussionmentioning

confidence: 99%

Neutron stars: From the inner crust to the core with the (extended) Nambu–Jona-Lasinio model

2016

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“…Although there is not still an accurate enough determination of NS radii, we have considered the constraint imposed by two recent studies on NS: a lower limit of R > 10.7 km for NS with masses M = 1.4 M established by Chen & Piekarewicz (2015), and an upper limit of R < 16.8 km, inferred from the NS RX J1856-375 Boshkayev et al (2016). The radii obtained for the CHS are within the range set by such limits.…”

Section: Structure Of Hybrid Starsmentioning

confidence: 99%

Constant entropy hybrid stars: a first approximation of cooling evolution

Mariani

Orsaria

Vucetich³

2017

A&A

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Aims. We aim to study the possibility of a hadron-quark phase transition in the interior of neutron stars, taking into account different schematic evolutionary stages at finite temperature. We also discuss the strange quark matter stability in the quark matter phase.Furthermore, we aim to analyze the astrophysical properties of hot and cold hybrid stars, considering the constraint on maximum mass given by the pulsars J1614-2230 and J0348+0432. Methods. We have developed a computational code to construct semi-analytical hybrid equations of state at fixed entropy per baryon and to obtain different families of hybrid stars. An analytical approximation of the Field Correlator Method is developed for the quark matter equation of state. For the hadronic equation of state we use a table based on the relativistic mean field theory, without hyperons. The phase transition was obtained imposing the Maxwell conditions, by assuming a high surface tension at the interface hadron-quark. We solved the relativistic structure equations of hydrostatic equilibrium and mass conservation for hybrid star configurations. Results. For the different equations of state obtained, we calculated the stability window for the strange quark matter, lepton abundances, temperature profiles and contours profiles for the maximum mass star depending on the parameters of the Field Correlator Method. We also computed the mass-radius and gravitational mass-baryonic mass relationships for different hybrid star families. Conclusions. We have analyzed different stages of hot hybrid stars as a first approximation of the cooling evolution of neutron stars with quark matter cores. We obtain cold hybrid stars with maximum masses ≥ 2M for different combinations of the Field Correlator Method parameters. In addition, our study based on the gravitational mass -baryonic mass plane shows a late phase transition between hadronic and quark matter during the proto-hybrid star evolution, in contrast with previous studies of proto-neutron stars.

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“…According to Ref. [7], an EOS with M max > 2M should produce R 1. 4 10.7 km in order to avoid being noncausal at highest NS densities.…”

Section: Introductionmentioning

confidence: 99%

Neutron star radii and crusts: Uncertainties and unified equations of state

Fortin¹,

Providência²,

Raduta³

et al. 2016

Phys. Rev. C

326

377

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The uncertainties in neutron star radii and crust properties due to our limited knowledge of the equation of state are quantitatively analyzed. We first demonstrate the importance of a unified microscopic description for the different baryonic densities of the star. If the pressure functional is obtained matching a crust and a core equation of state based on models with different properties at nuclear matter saturation, the uncertainties can be as large as ∼30 % for the crust thickness and 4% for the radius. Necessary conditions for causal and thermodynamically consistent matchings between the core and the crust are formulated and their consequences examined. A large set of unified equations of state for purely nucleonic matter is obtained based on twenty-four Skyrme interactions and nine relativistic mean-field nuclear parametrizations. In addition, for relativistic models fifteen equations of state including a transition to hyperonic matter at high density are presented. All these equations of state have in common the property of describing a 2M star and of being causal within stable neutron stars. Spans of ∼3 and ∼4 km are obtained for the radius of, respectively, 1.0M and 2.0M stars. Applying a set of nine further constraints from experiment and ab initio calculations the uncertainty is reduced to ∼1 and 2 km, respectively. These residual uncertainties reflect lack of constraints at large densities and insufficient information on the density dependence of the equation of state near the nuclear matter saturation point. The most important parameter to be constrained is shown to be the symmetry energy slope L. Indeed, this parameter exhibits a linear correlation with the stellar radius, which is particularly clear for small mass stars around 1.0M . The other equation-of-state parameters do not show clear correlations with the radius, within the present uncertainties. Potential constraints on L, the neutron star radius, and the equation of state from observations of thermal states of neutron stars are also discussed. The unified equations of state are made available in the Supplemental Materials and via the CompOSE database.

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Compactness of Neutron Stars

Cited by 72 publications

References 30 publications

Neutron stars: From the inner crust to the core with the (extended) Nambu–Jona-Lasinio model

Neutron stars: From the inner crust to the core with the (extended) Nambu–Jona-Lasinio model

Constant entropy hybrid stars: a first approximation of cooling evolution

Neutron star radii and crusts: Uncertainties and unified equations of state

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