scholarly journals Crystallization of the outer crust of a non-accreting neutron star

2020 ◽  
Vol 633 ◽  
pp. A149 ◽  
Author(s):  
A. F. Fantina ◽  
S. De Ridder ◽  
N. Chamel ◽  
F. Gulminelli
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Coupling Parameter ◽  
Equilibrium Composition ◽  
Nuclear Model ◽  
Self Consistent ◽  
Component Plasma ◽  
Rotational Evolution ◽  
The One ◽  
Outer Crust

Context. The interior of a neutron star is usually assumed to be made of cold catalyzed matter. However, the outer layers are unlikely to remain in full thermodynamic equilibrium during the formation of the star and its subsequent cooling, especially after crystallization occurs. Aims. We study the cooling and the equilibrium composition of the outer layers of a non-accreting neutron star down to crystallization. Here the impurity parameter, generally taken as a free parameter in cooling simulations, is calculated self-consistently using a microscopic nuclear model for which a unified equation of state has recently been determined. Methods. We follow the evolution of the nuclear distributions of the multi-component Coulomb liquid plasma fully self-consistently, adapting a general formalism originally developed for the description of supernova cores. We calculate the impurity parameter at the crystallization temperature as determined in the one-component plasma approximation. Results. Our analysis shows that the sharp changes in composition obtained in the one-component plasma approximation are smoothed out when a full nuclear distribution is allowed. The Coulomb coupling parameter at melting is found to be reasonably close to the canonical value of 175, except for specific values of the pressure for which supercooling occurs in the one-component plasma approximation. Our multi-component treatment leads to non-monotonic variations of the impurity parameter with pressure. Its values can change by several orders of magnitude reaching about 50, suggesting that the crust may be composed of an alternation of pure (highly conductive) and impure (highly resistive) layers. The results presented here complement the recent unified equation of state obtained within the same nuclear model. Conclusions. Our self-consistent approach to hot dense multi-component plasma shows that the presence of impurities in the outer crust of a neutron star is non-negligible and may have a sizeable impact on transport properties. In turn, this may have important implications not only for the cooling of neutron stars, but also for their magneto-rotational evolution.

scholarly journals Crystallization of the inner crust of a neutron star and the influence of shell effects

2020 ◽  
Vol 635 ◽  
pp. A84 ◽  
Author(s):  
T. Carreau ◽  
F. Gulminelli ◽  
N. Chamel ◽  
A. F. Fantina ◽  
J. M. Pearson
Keyword(s):  
Neutron Star ◽  
Finite Temperature ◽  
Nuclear Reactions ◽  
Compressible Liquid ◽  
Quantitative Prediction ◽  
Particle Structure ◽  
Shell Effects ◽  
Component Plasma ◽  
The One ◽  
Outer Crust

Context. In the cooling process of a non-accreting neutron star, the composition and properties of the crust are thought to be fixed at the finite temperature where nuclear reactions fall out of equilibrium. A lower estimate for this temperature is given by the crystallization temperature, which can be as high as ≈7 × 109 K in the inner crust, potentially leading to sizeable differences with respect to the simplifying cold-catalyzed matter hypothesis. Aims. We extend a recent work on the outer crust to the study of the crystallization of the inner crust and the associated composition in the one-component plasma approximation. Methods. The finite temperature variational equations for non-uniform matter in both the liquid and the solid phases are solved using a compressible liquid-drop approach with parameters optimized on four different microscopic models that cover current uncertainties in nuclear modeling. Results. We consider the effect of the different nuclear ingredients with their associated uncertainties separately: the nuclear equation of state, the surface properties in the presence of a uniform gas of dripped neutrons, and the proton shell effects arising from the ion single-particle structure. Our results suggest that the highest source of model dependence comes from the smooth part of the nuclear functional. Conclusions. We show that shell effects play an important role at the lowest densities close to the outer crust, but the most important physical ingredient to be settled for a quantitative prediction of the inner crust properties is the surface tension at extreme isospin values.

scholarly journals Neutron star equation of state and uncertainty on the radius determination

2017 ◽  
Vol 13 (S337) ◽  
pp. 225-228
Author(s):  
Morgane Fortin
Keyword(s):  
Experimental Data ◽  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Nuclear Model ◽  
Large Collection ◽  
X Ray ◽  
The Core ◽  
Simultaneous Measurements ◽  
New Generation

AbstractSimultaneous measurements of the radius and mass of neutron stars (NSs) are expected from the new generation of X-ray telescopes, potentially constraining the NS equation of state (EoS). However using ‘non-unified’ EoSs with the ones for the core and the crust not based on the same nuclear model can introduce an uncertainty on the radius as large as the precision expected from these instruments. I present two solutions to this problem: a large collection of unified EoSs and an approximate and yet precise approach that, with no need of a crust EoS, provides the relation between the NS mass and radius. I discuss correlations between the NS radius and nuclear parameters, possibly allowing to constrain the NS radius with experiments on Earth. Finally, I show that in spite of the observation of massive NSs, one can not exclude that hyperons appear at high densities in NSs due to the scarcity of the available experimental data.

COSMOLOGICAL SOLUTION IN THE BRANE WITH GAUSS–BONNET GRAVITY IN THE BULK

2009 ◽  
Vol 24 (24) ◽  
pp. 1915-1923 ◽  
Author(s):  
SUBENOY CHAKRABORTY ◽  
TANWI BANDYOPADHYAY
Keyword(s):  
Equation Of State ◽  
Coupling Parameter ◽  
Cosmological Solution ◽  
Chaplygin Gas ◽  
Modified Chaplygin Gas ◽  
Bonnet Gravity ◽  
Cosmological Solutions ◽  
Barotropic Equation ◽  
Five Dimension ◽  
The One

The paper deals with Gauss–Bonnet gravity in five dimension without a Cosmological Constant and the coupling parameter is taken to be negative. Cosmological solutions are obtained for both bulk and the brane. The matter in the brane is chosen in the form of perfect fluid with barotropic equation of state (except the one with Modified Chaplygin Gas, which is not solvable) and the solutions are consistent with the recent observations.

scholarly journals Inner crust of a neutron star at the point of crystallization in a multicomponent approach

2020 ◽  
Vol 640 ◽  
pp. A77 ◽  
Author(s):  
T. Carreau ◽  
A. F. Fantina ◽  
F. Gulminelli
Keyword(s):  
Neutron Star ◽  
Crystallization Temperature ◽  
Thermal Evolution ◽  
Energy Functional ◽  
Compressible Liquid ◽  
Quantitative Prediction ◽  
Nuclear Models ◽  
Component Plasma ◽  
Fast Cooling ◽  
The One

Context. The possible presence of amorphous and heterogeneous phases in the inner crust of a neutron star is expected to reduce the electrical conductivity of the crust, potentially with significant consequences on the magneto-thermal evolution of the star. In cooling simulations, the disorder is quantified by an impurity parameter, which is often taken as a free parameter. Aims. We aim to give a quantitative prediction of the impurity parameter as a function of the density in the crust, performing microscopic calculations including up-to-date microphysics of the crust. Methods. A multicomponent approach was developed at a finite temperature using a compressible liquid-drop description of the ions with an improved energy functional based on recent microscopic nuclear models and optimized on extended Thomas-Fermi calculations. Thermodynamic consistency was ensured by adding a rearrangement term, and deviations from the linear mixing rule were included in the liquid phase. Results. The impurity parameter is consistently calculated at the crystallization temperature as determined in the one-component plasma approximation for the different functionals. Our calculations show that at the crystallization temperature, the composition of the inner crust is dominated by nuclei with charge number around Z ≈ 40, while the range of the Z distribution varies from about 20 near the neutron drip to about 40 closer to the crust-core transition. This reflects on the behavior of the impurity parameter that monotonically increases with density reaching up to around 40 in the deeper regions of the inner crust. Conclusions. Our study shows that the contribution of impurities is non-negligible, thus potentially having an impact on the transport properties in the neutron-star crust. The obtained values of the impurity parameter represent a lower limit; larger values are expected in the presence of nonspherical geometries and/or fast cooling dynamics.

Equation of state of the one-component plasma derived from precision Monte Carlo calculations

1990 ◽  
Vol 41 (2) ◽  
pp. 1105-1111 ◽  
Author(s):  
Guy S. Stringfellow ◽  
Hugh E. DeWitt ◽  
W. L. Slattery
Keyword(s):  
Monte Carlo ◽  
Equation Of State ◽  
Monte Carlo Calculations ◽  
Component Plasma ◽  
The One
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