A possible representation for the neutron star PSR J0437-4715

Estevez-Delgado, Joaquin; Cleary-Balderas, Arthur; Murguía, Aurelio Tamez; Soto-Espitia, Rafael

doi:10.1140/epjp/i2019-12919-0

Cited by 25 publications

(9 citation statements)

References 33 publications

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“…A lot of anisotropic solutions and anisotropic compact star models have been proposed and studied [22][23][24][25][26][27][28][29][30][31][32]. Ivanov has calculated general bounds on the redshift for any anisotropic compact star in Ref.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic neutron stars modelling: constraints in Krori–Barua spacetime

Roupas

Nashed

2020

Eur. Phys. J. C

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Dense nuclear matter is expected to be anisotropic due to effects such as solidification, superfluidity, strong magnetic fields, hyperons, pion-condensation. Therefore an anisotropic neutron star core seems more realistic than an ideally isotropic one. We model anisotropic neutron stars working in the Krori–Barua (KB) ansatz without preassuming an equation of state. We show that the physics of general KB solutions is encapsulated in the compactness. Imposing physical and stability requirements yields a maximum allowed compactness $$2GM/Rc^2 < 0.71$$ 2 G M / R c 2 < 0.71 for a KB-spacetime. We further input observational data from numerous pulsars and calculate the boundary density. We focus especially on data from the LIGO/Virgo collaboration as well as recent independent measurements of mass and radius of miilisecond pulsars with white dwarf companions by the Neutron Star Interior Composition Explorer (NICER). For these data the KB-spacetime gives the same boundary density which surprisingly equals the nuclear saturation density within the data precision. Since this value designates the boundary of a neutron core, the KB-spacetime applies naturally to neutron stars. For this boundary condition we calculate a maximum mass of 4.1 solar masses.

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Section: Introductionmentioning

confidence: 99%

Anisotropic neutron stars modelling: constraints in Krori–Barua spacetime

Roupas

Nashed

2020

Eur. Phys. J. C

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“…On the other hand there have been some approaches at a stellar level to describe compact objects [20][21][22][23], considering that the interior of the stars is formed by ordinary neutral matter [24][25][26][27][28][29][30], ordinary charged matter [31][32][33][34][35][36][37], and also by sources which are a combination of ordinary matter and quintessence dark energy, consistent with neutron stars [38]. Neutron or quark stars are not exclusively composed of neutrons or quarks, respectively, but rather these stars are formed predominantly by one of those particles.…”

Section: Introductionmentioning

confidence: 99%

On quintessence star model and strange star

Estevez-Delgado

2020

Eur. Phys. J. C

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The astronomical observations on the accelerated expansion of the universe generate the possibility that the internal matter of the stars is not only formed by ordinary matter but also by matter with negative pressure. We discuss the existence of stars formed by the coexistence of two types of fluids, one associated to quintessence dark matter described by the radial and tangential pressures $$(P_{rq},P_{tq})$$ ( P rq , P tq ) and the density $$\rho _{q}$$ ρ q characterized by a parameter $$-1<w<-\frac{1}{3}$$ - 1 < w < - 1 3 and ordinary matter described by an anisotropic fluid with radial pressure of a strange star given by the MIT Bag model $$P_r=\frac{1}{3}(c^2\rho -4B_g)$$ P r = 1 3 ( c 2 ρ - 4 B g ) and tangential pressure $$P_t=\frac{1}{3}(c^2\rho -4B_g)-\frac{3}{2}(1+w)c^2\rho _q$$ P t = 1 3 ( c 2 ρ - 4 B g ) - 3 2 ( 1 + w ) c 2 ρ q , in which the effect is reflected of the quintessence dark matter over the ordinary matter. Via a theorem we show that the geometry that describes this interaction is equivalent to that of a perfect fluid with ordinary matter. Taking as geometry the one associated with a model for neutron stars, a physically acceptable and stable model is obtained. The application to the star Her X-1, as a candidate to a strange quark star, generates for us a value of the MIT Bag constant $$B_g = 97.0048\,\mathrm{Mev}/\mathrm{fm}^3$$ B g = 97.0048 Mev / fm 3 , which is found to be inside the expected interval.

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“…The maximum mass of anisotropic compact neutron stars has been estimated to be M max ∼ 4M ⊙ [30]. Several anisotropic solutions include Refs [47][48][49][50][51][52][53][54][55][56][57][58].…”

Section: Introductionmentioning

confidence: 99%

Secondary component of gravitational-wave signal GW190814 as an anisotropic neutron star

Roupas

2020

Preprint

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The gravitational-wave signal GW190814 involves a compact object with mass (2.50 − 2.67)M⊙ within the so-called low mass gap. As yet, a general consensus on its nature, being a black hole, a neutron star or an exotic star, has not been achieved. We investigate the possibility this compact object to be an anisotropic neutron star. Anisotropies in a neutron star core arise naturally by effects such as superfluidity, hyperons, strong magnetic fields and allow the maximum mass to exceed that of the ideally isotropic stars. We consider the Krori-Barua ansatz to model an anisotropic core and constrain the equation of state with LIGO/Virgo observations GW170817 and GW190814. We find that the GW190814 secondary component can be an anisotropic neutron star compatible with LIGO/Virgo constraints if the radius attains a value in the range (13.2 − 14.0) km with the anisotropic core's boundary density in the range (3.5 − 4.0) • 10 14 g/cm 3 .

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A possible representation for the neutron star PSR J0437-4715

Cited by 25 publications

References 33 publications

Anisotropic neutron stars modelling: constraints in Krori–Barua spacetime

Anisotropic neutron stars modelling: constraints in Krori–Barua spacetime

On quintessence star model and strange star

Secondary component of gravitational-wave signal GW190814 as an anisotropic neutron star

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