NEUTRON STAR EVOLUTIONS USING NUCLEAR EQUATIONS OF STATE WITH A NEW EXECUTION MODEL

Background. We investigate possible correlations between neutron star observables and properties of atomic nuclei. In particular, we explore how the tidal deformability of a 1.4 solar mass neutron star, M1.4, and the neutron-skin thickness of 48Ca and 208Pb are related to the stellar radius and the stiffness of the symmetry energy. Methods. We examine a large set of nuclear equations of state based on phenomenological models (Skyrme, NLWM, DDM) and ab initio theoretical methods (BBG, Dirac–Brueckner, Variational, Quantum Monte Carlo). Results: We find strong correlations between tidal deformability and NS radius, whereas a weaker correlation does exist with the stiffness of the symmetry energy. Regarding the neutron-skin thickness, weak correlations appear both with the stiffness of the symmetry energy, and the radius of a M1.4. Our results show that whereas the considered EoS are compatible with the largest masses observed up to now, only five microscopic models and four Skyrme forces are simultaneously compatible with the present constraints on L and the PREX experimental data on the 208Pb neutron-skin thickness. We find that all the NLWM and DDM models and the majority of the Skyrme forces are excluded by these two experimental constraints, and that the analysis of the data collected by the NICER mission excludes most of the NLWM considered. Conclusion. The tidal deformability of a M1.4 and the neutron-skin thickness of atomic nuclei show some degree of correlation with nuclear and astrophysical observables, which however depends on the ensemble of adopted EoS.

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Estimation of Electrical Conductivity and Magnetization Parameter of Neutron Star Crusts and Applied to the High-Braking-Index Pulsar PSR J1640-4631

Universe ◽

10.3390/universe6050063 ◽

2020 ◽

Vol 6 (5) ◽

pp. 63

Author(s):

Hui Wang ◽

Zhi-Fu Gao ◽

Huan-Yu Jia ◽

Na Wang ◽

Xiang-Dong Li

Keyword(s):

Magnetic Field ◽

Neutron Star ◽

Neutron Stars ◽

General Expression ◽

Equations Of State ◽

Rotation Period ◽

Ohmic Dissipation ◽

Hartree Fock ◽

Induction Equation ◽

The Magnetic Field

Young pulsars are thought to be highly magnetized neutron stars (NSs). The crustal magnetic field of a NS usually decays at different timescales in the forms of Hall drift and Ohmic dissipation. The magnetization parameter ω B τ is defined as the ratio of the Ohmic timescale τ O h m to the Hall drift timescale τ H a l l . During the first several million years, the inner temperature of the newly born neutron star cools from T = 10 9 K to T = 1.0 × 10 8 K, and the crustal conductivity increases by three orders of magnitude. In this work, we adopt a unified equations of state for cold non-accreting neutron stars with the Hartree–Fock–Bogoliubov method, developed by Pearson et al. (2018), and choose two fiducial dipole magnetic fields of B = 1.0 × 10 13 G and B = 1.0 × 10 14 G, four different temperatures, T, and two different impurity concentration parameters, Q, and then calculate the conductivity of the inner crust of NSs and give a general expression of magnetization parameter for young pulsars: ω B τ ≃ ( 1 − 50 ) B 0 / ( 10 13 G) by using numerical simulations. It was found when B ≤ 10 15 G, due to the quantum effects, the conductivity increases slightly with the increase in the magnetic field, the enhanced magnetic field has a small effect on the matter in the low-density regions of the crust, and almost has no influence the matter in the high-density regions. Then, we apply the general expression of the magnetization parameter to the high braking-index pulsar PSR J1640-4631. By combining the observed arrival time parameters of PSR J1640-4631 with the magnetic induction equation, we estimated the initial rotation period P 0 , the initial dipole magnetic field B 0 , the Ohm dissipation timescale τ O h m and Hall drift timescale τ H a l l . We model the magnetic field evolution and the braking-index evolution of the pulsar and compare the results with its observations. It is expected that the results of this paper can be applied to more young pulsars.

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CONSTRAINING MODELS OF TWIN-PEAK QUASI-PERIODIC OSCILLATIONS WITH REALISTIC NEUTRON STAR EQUATIONS OF STATE

The Astrophysical Journal ◽

10.3847/1538-4357/833/2/273 ◽

2016 ◽

Vol 833 (2) ◽

pp. 273 ◽

Cited By ~ 7

Author(s):

Gabriel Török ◽

Kateřina Goluchová ◽

Martin Urbanec ◽

Eva Šrámková ◽

Karel Adámek ◽

...

Keyword(s):

Neutron Star ◽

Equations Of State ◽

Periodic Oscillations ◽

Twin Peak

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Fundamental physics and the absence of sub-millisecond pulsars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833521 ◽

2018 ◽

Vol 620 ◽

pp. A69 ◽

Cited By ~ 4

Author(s):

B. Haskell ◽

J. L. Zdunik ◽

M. Fortin ◽

M. Bejger ◽

R. Wijnands ◽

...

Keyword(s):

Neutron Star ◽

Equation Of State ◽

Neutron Stars ◽

Gravitational Wave ◽

Equations Of State ◽

Rotation Frequency ◽

Hadronic Matter ◽

Spin Distribution ◽

Test Models ◽

State Of Matter

Context. Rapidly rotating neutron stars are an ideal laboratory to test models of matter at high densities. In particular, the maximum rotation frequency of a neutron star depends on the equation of state and can be used to test models of the interior. However, observations of the spin distribution of rapidly rotating neutron stars show evidence for a lack of stars spinning at frequencies higher than f ≈ 700 Hz, well below the predictions of theoretical equations of state. This has generally been taken as evidence of an additional spin-down torque operating in these systems, and it has been suggested that gravitational wave torques may be operating and be linked to a potentially observable signal. Aims. We aim to determine whether additional spin-down torques (possibly due to gravitational wave emission) are necessary, or if the observed limit of f ≈ 700 Hz could correspond to the Keplerian (mass-shedding) break-up frequency for the observed systems, and is simply a consequence of the currently unknown state of matter at high densities. Methods. Given our ignorance with regard to the true equation of state of matter above nuclear saturation densities, we make a minimal physical assumption and only demand causality, that is, that the speed of sound in the interior of the neutron star should be lower than or equal to the speed of light c. We then connected our causally limited equation of state to a realistic microphysical crustal equation of state for densities below nuclear saturation density. This produced a limiting model that gave the lowest possible maximum frequency, which we compared to observational constraints on neutron star masses and frequencies. We also compared our findings with the constraints on the tidal deformability obtained in the observations of the GW170817 event. Results. We rule out centrifugal breakup as the mechanism preventing pulsars from spinning faster than f ≈ 700 Hz, as the lowest breakup frequency allowed by our causal equation of state is f ≈ 1200 Hz. A low-frequency cutoff, around f ≈ 800 Hz could only be possible when we assume that these systems do not contain neutron stars with masses above M ≈ 2 M⊙. This would have to be due either to selection effects, or possibly to a phase transition in the interior of the neutron star that leads to softening at high densities and a collapse to either a black hole or a hybrid star above M ≈ 2 M⊙. Such a scenario would, however, require a somewhat unrealistically stiff equation of state for hadronic matter, in tension with recent constraints obtained from gravitational wave observations of a neutron star merger.

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Relativistic neutron star merger simulations with non-zero temperature equations of state

Astronomy and Astrophysics ◽

10.1051/0004-6361:20066682 ◽

2007 ◽

Vol 467 (2) ◽

pp. 395-409 ◽

Cited By ~ 152

Author(s):

R. Oechslin ◽

H.-T. Janka ◽

A. Marek

Keyword(s):

Neutron Star ◽

Equations Of State ◽

Zero Temperature

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Constraints on Microscopic and Phenomenological Equations of State of Dense Matter from GW170817

Universe ◽

10.3390/universe5100204 ◽

2019 ◽

Vol 5 (10) ◽

pp. 204 ◽

Cited By ~ 1

Author(s):

Domenico Logoteta ◽

Ignazio Bombaci

Keyword(s):

Neutron Star ◽

Neutron Stars ◽

Equations Of State ◽

Mean Field ◽

Dense Matter ◽

Neutron Star Matter ◽

Field Approach ◽

Relativistic Mean Field ◽

Three Body ◽

Good Agreement

We discuss the constraints on the equation of state (EOS) of neutron star matter obtained by the data analysis of the neutron star-neutron star merger in the event GW170807. To this scope, we consider two recent microscopic EOS models computed starting from two-body and three-body nuclear interactions derived using chiral perturbation theory. For comparison, we also use three representative phenomenological EOS models derived within the relativistic mean field approach. For each model, we determine the β -stable EOS and then the corresponding neutron star structure by solving the equations of hydrostatic equilibrium in general relativity. In addition, we calculate the tidal deformability parameters for the two neutron stars and discuss the results of our calculations in connection with the constraints obtained from the gravitational wave signal in GW170817. We find that the tidal deformabilities and radii for the binary’s component neutron stars in GW170817, calculated using a recent microscopic EOS model proposed by the present authors, are in very good agreement with those derived by gravitational waves data.

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The Bologna submillisecond pulsar survey

International Astronomical Union Colloquium ◽

10.1017/s0252921100058905 ◽

2000 ◽

Vol 177 ◽

pp. 27-30 ◽

Cited By ~ 1

Author(s):

Nichi D’Amico

Keyword(s):

Neutron Star ◽

Large Scale ◽

Equations Of State ◽

The Other ◽

Millisecond Pulsar ◽

Millisecond Pulsars ◽

Spin Period ◽

Other Hand

AbstractSince the discovery of the original millisecond pulsar, no pulsars with a shorter spin period (P<1.56 ms) were found. However, according to the most popular equations of state, the theoretical limiting spin period of a neutron star can be much shorter. On the other hand, most of the large scale searches for millisecond pulsars carried out so far were strongly biased against the detection of ultrashort periodicities. In this paper we describe a new large scale pulsar survey with a minimum detectable period much shorter than previous searches.

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COMPUTATION OF NEUTRON STAR STRUCTURE USING MODERN EQUATION OF STATE

International Journal of Modern Physics A ◽

10.1142/s0217751x06028400 ◽

2006 ◽

Vol 21 (07) ◽

pp. 1555-1565 ◽

Cited By ~ 16

Author(s):

G. H. BORDBAR ◽

M. HAYATI

Keyword(s):

Neutron Star ◽

Equation Of State ◽

Equations Of State ◽

Maximum Mass ◽

Neutron Star Matter ◽

Radio Pulsars ◽

Good Consistency ◽

The Given ◽

Neutron Star Radius ◽

Star Structure

Using the modern equations of state derived from microscopic calculations, we have calculated the neutron star structure. For the neutron star, we have obtained a minimum mass about 0.1 M⊙ which is nearly independent of the equation of state, and a maximum mass between 1.47 M⊙ and 1.98 M⊙ which is strongly dependent on the equation of state. It is shown that among the equations of state of neutron star matter which we have used, the stiffest one leads to higher maximum mass and radius and lower central density. It is seen that the given maximum mass for the Reid-93 equation of state shows a good consistency with the accurate observations of radio pulsars. We have indicated that the thickness of neutron star crust is very small compared to the predicted neutron star radius.

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