The Study of Magnetically Deformed Atoms in the Outer Crust of Neutron Stars in Presence of Strong Quantizing Magnetic Field (original) (raw)
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Inner Crusts of Neutron Stars in Strongly Quantizing Magnetic Fields
The Astrophysical Journal, 2011
We study the properties and stability of nuclei in the inner crust of neutron stars in the presence of strong magnetic fields ∼ 10 17 G. Nuclei coexist with a neutron gas and reside in a uniform gas of electrons in the inner crust. This problem is investigated within the Thomas-Fermi model. We extract the properties of nuclei based on the subtraction procedure of Bonche, Levit and Vautherin. The phase space modification of electrons due to Landau quantisation in the presence of strong magnetic fields leads to the enhancement of electron as well as proton fractions at lower densities ∼ 0.001 fm −3. We find the equilibrium nucleus at each average baryon density by minimising the free energy and show that ,in the presence of strong magnetic fields, it is lower than that in the field free case. The size of the spherical cell that encloses a nucleus along with the neutron and electron gases becomes smaller in strong magnetic fields compared with the zero field case. Nuclei with larger mass and atomic numbers are obtained in the presence of strong magnetic fields as compared with cases of zero field.
We have investigated some of the properties of dense sub-nuclear matter at the crustal region (both the outer crust and the inner crust region) of a magnetar. The relativistic version of Thomas-Fermi (TF) model is used in presence of strong quantizing magnetic field for the outer crust matter. The compressed matter in the outer crust, which is a crystal of metallic iron, is replaced by a regular array of spherically symmetric Wigner-Seitz (WS) cells. In the inner crust region, a mixture of iron and heavier neutron rich nuclei along with electrons and free neutrons has been considered. Conventional Harrison-Wheeler (HW) and Bethe-Baym-Pethick (BBP) equation of states are used for the nuclear mass formula. A lot of significant changes in the characteristic properties of dense crustal matter, both at the outer crust and the inner crust, have been observed. Comment: 20 pages, 11 .eps figures, to appear in EPJA
Different Magnetic Field Distributions in Deformed Neutron Stars
2019
In this work, we review the formalism which would allow us to model magnetically deformed neutron stars. We study the effect of different magnetic field configurations on the equation of state (EoS) and the structure of such stars. For this aim, the EoS of magnetars is acquired by using the lowest order constraint variational (LOCV) method and employing the AV18 potential. We show how the magnetic field varies from the surface to the center of neutron star by using various exponential and polynomial profiles and compare their results.In addition, global properties of neutron stars are obtained within two formalisms. The first formalism is described by considering the pressure into two directions and the deformation of neutron stars is governed by anisotropies in the equation of state. The second formalism for investigating macroscopic properties of magnetars is gained by treating the nonuniform pressure as a perturbation to the tota...
Structure and deformations of strongly magnetized neutron stars with twisted-torus configurations
Monthly Notices of the Royal Astronomical Society, 2010
We construct general relativistic models of stationary, strongly magnetized neutron stars. The magnetic field configuration, obtained by solving the relativistic Grad-Shafranov equation, is a generalization of the twisted torus model recently proposed in the literature; the stellar deformations induced by the magnetic field are computed by solving the perturbed Einstein's equations; stellar matter is modeled using realistic equations of state. We find that in these configurations the poloidal field dominates over the toroidal field and that, if the magnetic field is sufficiently strong during the first phases of the stellar life, it can produce large deformations.
The Astrophysical Journal, 1998
We present numerical calculations of the equation of state for dense matter in high magnetic fields, using a temperature dependent Thomas-Fermi theory with a magnetic field that takes all Landau levels into account. Free energies for atoms and matter are also calculated as well as profiles of the electron density as a function of distance from the atomic nucleus for representative values of the magnetic field strength, total matter density, and temperature. The Landau shell structure, which is so prominent in cold dense matter in high magnetic fields, is still clearly present at finite temperature as long as it is less than approximately one tenth of the cyclotron energy. This structure is reflected in an oscillatory behaviour of the equation of state and other thermodynamic properties of dense matter and hence also in profiles of the density and pressure as functions of depth in the surface layers of magnetic neutron stars. These oscillations are completely smoothed out by thermal effects at temperatures of the order of the cyclotron energy or higher.
Deformation of a magnetized neutron star
Physical Review C, 2014
Magnetars are compact stars which are observationally determined to have a very strong surface magnetic fields of the order of 10 14 − 10 15 G. The centre of the star can even have a magnetic field several orders of magnitude larger. We study the effect of the magnetic field on the mass and shape of such a star. In general, we assume a non-uniform magnetic field inside the star which varies with density. The magnetic energy and magnetic pressure as well as the metric are expanded as multipoles in spherical harmonics up to the quadrupole term to the total energy and pressure.
Physical Review C, 2012
The equilibrium properties of the outer crust of cold nonaccreting magnetars (i.e. neutron stars endowed with very strong magnetic fields) are studied using the latest experimental atomic mass data complemented with a microscopic atomic mass model based on the Hartree-Fock-Bogoliubov method. The Landau quantization of electron motion caused by the strong magnetic field is found to have a significant impact on the composition and the equation of state of crustal matter. It is also shown that the outer crust of magnetars could be much more massive than that of ordinary neutron stars.
Relativistic models of magnetars: structure and deformations
Monthly Notices of the Royal Astronomical Society, 2008
We find numerical solutions of the coupled system of Einstein-Maxwell's equations with a linear approach, in which the magnetic field acts as a perturbation of a spherical neutron star. In our study, magnetic fields having both poloidal and toroidal components are considered, and higher order multipoles are also included. We evaluate the deformations induced by different field configurations, paying special attention to those for which the star has a prolate shape. We also explore the dependence of the stellar deformation on the particular choice of the equation of state and on the mass of the star. Our results show that, for neutron stars with mass M = 1.4 M⊙ and surface magnetic fields of the order of 10 15 G, a quadrupole ellipticity of the order of 10 −6 − 10 −5 should be expected. Low mass neutron stars are in principle subject to larger deformations (quadrupole ellipticities up to 10 −3 in the most extreme case). The effect of quadrupolar magnetic fields is comparable to that of dipolar components. A magnetic field permeating the whole star is normally needed to obtain negative quadrupole ellipticities, while fields confined to the crust typically produce positive quadrupole ellipticities.
Effects of Strong Magnetic Fields on the Equation of State of Cold Non-Accreting Neutron-Star Crusts
2011
Using the latest experimental atomic mass data complemented with a microscopic atomic mass model, we have determined the equilibrium structure of the outer crust of cold non-accreting neutron stars endowed with strong magnetic fields. The equation of state is found to be markedly affected by the Landau quantization of electron motion. In particular, a strongly quantizing magnetic field not only changes the crust composition but also makes the crust more incompressible.
Many Aspects of Magnetic Fields in Neutron Stars
Universe, 2018
In this work, we explore different aspects in which strong magnetic fields play a role in the composition, structure and evolution of neutron stars. More specifically, we discuss (i) how strong magnetic fields change the equation of state of dense matter, alter its composition, and create anisotropies, (ii) how they change the structure of neutron stars (such mass and radius) and the formalism necessary to calculate those changes, and (iii) how they can affect neutron stars' evolution. In particular, we focus on how a time-dependent magnetic field modifies the cooling of a special group known as X-ray dim neutron stars.