Liquid Drop Model for Investigating the Outer Crust of Neutron Star

The properties of outer crust of cooling neutron star by using Liquid Drop Model approximation has been studied. Th is mass model is used to derive the properties of outer crust of neutron star matter such as total energy of system, equation of state (relationship between pressure and density), and composition of the outer crust. The properties of the outer crust are studied under the assumption that neutron star has created for long time and the matter in neutron star is in its ground state. The composition of the outer crust consists of ions Z arranged in a lattice and free electrons e, so that the total energy of the system consists of three contributions: the mass-energy of the nuclear, the energy of electrons and lattice. The equation of state (the relationship between pressure and density) shows that the pressure increases with increasing density in the outer crust layer. With a simple model based on liquid drop model, it is known that the outer crust is composed of nuclei which are at Z ≈ 20-50, with 56Fe core at the upper layer, and 154Cd core at the lowermost layer of the outer crust.

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The Study of Symmetry Energy in Pasta of Neutron Star From Compressible Liquid Drop Model Approximation

Proceeding International Conference on Science and Engineering ◽

10.14421/icse.v2.56 ◽

2019 ◽

Vol 2 ◽

pp. 61-72

Author(s):

Eko Tri Sulistyani ◽

Rizky Ananda

Keyword(s):

Neutron Star ◽

Symmetry Energy ◽

Liquid Drop ◽

Compressible Liquid ◽

Bonding Energy ◽

Liquid Drop Model ◽

Model Approximation ◽

Protons And Neutrons ◽

Seitz Cell ◽

Neutron Pair

The properties of pasta which is located at the bottom of inner crust from neutron star has been studied by using compressibl e liquid drop model. Compressible liquid drop model is a modified liquid drop model as a density function. Liquid drop model based on assumption that the magnitude of nucleus bonding energy is contribution of surface, Coulomb, volume, symmetry, and proton -neutron pair effect. Pasta of neutron star behaves like liquid crystals (mesomhorpic phase). The top layer of pasta filled by free neutron gas, while in the lowest layer of the pasta is filled by proton-neutron gas. The properties of pasta are observed at temperatures close to zero Kelvin with the assumption that neutron star is on ground state and non accretion. The study of pasta emphasizes on symmetry energy’s influence. Symmetry energy reduces the magnitude of bonding energy of nucleon in the nucleus and it causes nucleon to be more easily released from nucleus. After that, symmetry energy influence the properties of pasta, such as the shape of nucleus that is non spherical (some like plates, rods, and bubbles), the fluctuative values of Wigner-Seitz cell, and uneven distribution of protons and neutrons in the pasta region of neutron star.

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Non-spherical nucleon clusters in the mantle of a neutron star: CLDM based on Skyrme-type forces

Journal of Physics Conference Series ◽

10.1088/1742-6596/2103/1/012004 ◽

2021 ◽

Vol 2103 (1) ◽

pp. 012004

Author(s):

N A Zemlyakov ◽

A I Chugunov ◽

N N Shchechilin

Keyword(s):

Neutron Star ◽

Nuclear Matter ◽

Liquid Drop ◽

Outer Region ◽

Spherical Shape ◽

Baryon Number ◽

Compressible Liquid ◽

Liquid Drop Model ◽

The Core ◽

Nuclear Clusters

Abstract Neutron stars are superdense compact astrophysical objects. The central region of the neuron star (the core) consists of locally homogeneous nuclear matter, while in the outer region (the crust) nucleons are clustered. In the outer crust these nuclear clusters represent neutron-rich atomic nuclei and all nucleons are bound within them. Whereas in the inner crust some neutrons are unbound, but nuclear clusters still keeps generally spherical shape. Here we consider the region between the crust and the core of the star, so-called mantle, where non-spherical nuclear clusters may exist. We apply compressible liquid drop model to calculate the energy density for several shape types of nuclear clusters. It allows us to identify the most energetically favorable configuration as function of baryon number density. Employing four Skyrme-type forces (SLy4 and BSk24, BSk25, BSk26), which are widely used in the neutron star physics, we faced with strong model dependence of the ground state composition. In particular, in agreement with previous works within liquid drop model, mantle is absent for SLy4 (nuclear spheres directly transit into homogeneous nuclear matter; exotic nuclear shapes do not appear).

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The isotherms of an imperfect gas

Mathematical Proceedings of the Cambridge Philosophical Society ◽

10.1017/s0305004100028127 ◽

1953 ◽

Vol 49 (1) ◽

pp. 130-135 ◽

Cited By ~ 6

Author(s):

D. ter Haar

Keyword(s):

Equation Of State ◽

General Model ◽

General Type ◽

Liquid Drop ◽

Liquid Drop Model ◽

Imperfect Gas ◽

The One ◽

Different Parts ◽

Number Of Particles

ABSTRACTThe liquid drop model of an imperfect gas in the form introduced by Wergeland is discussed by using the method of the grand ensembles and the equation of state of the system is derived. This equation of state is of the same general type as the one derived by Mayer for a more general model. It is shown that in both cases the isotherms consist of two analytically different parts in the limit where the number of particles in the system, N, goes to infinity.

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

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936359 ◽

2020 ◽

Vol 633 ◽

pp. A149 ◽

Cited By ~ 6

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.

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R-mode constraints from neutron star equation of state

HNPS Proceedings ◽

10.12681/hnps.1913 ◽

2019 ◽

Vol 23 ◽

pp. 100

Author(s):

Ch. C. Moustakidis ◽

M. C. Papazoglou

Keyword(s):

Neutron Star ◽

Equation Of State ◽

Neutron Stars ◽

Gravitational Radiation ◽

Mode Instability ◽

X Ray ◽

Long Time ◽

Low Mass ◽

X Ray Binaries

The gravitational radiation has been proposed a long time before, as an explana- tion for the observed relatively low spin frequencies of young neutron stars and of accreting neutron stars in low-mass X-ray binaries as well. In the present work we studied the effects of the neutron star equation of state on the r-mode instability window of rotating neutron stars.

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