Microscopic vortex velocity in the inner crust and outer core of neutron stars

Temperature and velocity-dependent 1S0 pairing gaps, chemical potentials and entrainment matrix in dense homogeneous neutron–proton superfluid mixtures constituting the outer core of neutron stars, are determined fully self-consistently by solving numerically the time-dependent Hartree–Fock–Bogoliubov equations over the whole range of temperatures and flow velocities for which superfluidity can exist. Calculations have been made for npeμ in beta-equilibrium using the Brussels–Montreal functional BSk24. The accuracy of various approximations is assessed and the physical meaning of the different velocities and momentum densities appearing in the theory is clarified. Together with the unified equation of state published earlier, the present results provide consistent microscopic inputs for modeling superfluid neutron-star cores.

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Vortex pinning in the superfluid core of relativistic neutron stars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab606 ◽

2021 ◽

Vol 503 (1) ◽

pp. 1407-1417

Author(s):

Aurélien Sourie ◽

Nicolas Chamel

Keyword(s):

Neutron Stars ◽

Outer Core ◽

Vortex Pinning ◽

Global Dynamics ◽

Mutual Friction ◽

Dynamical Equations ◽

General Relativistic ◽

Superfluid Core ◽

Relativistic Framework

ABSTRACT Our recent Newtonian treatment of the smooth-averaged mutual-friction force acting on the neutron superfluid and locally induced by the pinning of quantized neutron vortices to proton fluxoids in the outer core of superfluid neutron stars is here adapted to the general-relativistic framework. We show how the local non-relativistic motion of individual vortices can be matched to the global dynamics of the star using the fully 4D covariant Newtonian formalism of Carter & Chamel. We derive all the necessary dynamical equations for carrying out realistic simulations of superfluid rotating neutron stars in full general relativity, as required for the interpretation of pulsar frequency glitches. The role of vortex pinning on the global dynamics appears to be non-trivial.

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Oscillatory superfluid Ekman pumping in helium II and neutron stars

Journal of Fluid Mechanics ◽

10.1017/jfm.2015.553 ◽

2015 ◽

Vol 783 ◽

pp. 251-282 ◽

Cited By ~ 2

Author(s):

C. Anthony van Eysden

Keyword(s):

Neutron Stars ◽

Low Frequency ◽

Line Tension ◽

Outer Core ◽

Oscillation Period ◽

Analytic Solutions ◽

Ekman Pumping ◽

Helium Ii ◽

Tension Parameter ◽

Pumping Mode

The linear response of a superfluid, rotating uniformly in a cylindrical container and threaded with a large number of vortex lines, to an impulsive increase in the angular velocity of the container is investigated. At zero temperature and with perfect pinning of vortices to the top and bottom of the container, we demonstrate that the system oscillates persistently with a frequency proportional to the vortex line tension parameter to the quarter power. This low-frequency mode is generated by a secondary flow analogous to classical Ekman pumping that is periodically reversed by the vortex tension in the boundary layers. We compare analytic solutions to the two-fluid equations by Chandler & Baym (J. Low Temp. Phys., vol. 62, 1986, pp. 119–142) with the spin-up experiments by Tsakadze & Tsakadze (J. Low Temp. Phys., vol. 39, 1980, pp. 649–688) in helium II and find that the frequency agrees within a factor of four, although the experiment is not perfectly suited to the application of linear theory. We argue that this oscillatory Ekman pumping mode, and not Tkachenko modes, provides a natural explanation for the observed oscillation. In neutron stars, the oscillation period depends on the pinning interaction between neutron vortices and flux tubes in the outer core. Using a simplified pinning model, we demonstrate that strong pinning can accommodate modes with periods of days to years, which are only weakly damped by mutual friction over longer time scales.

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QUASI-STATIONARY ELECTROMAGNETIC EFFECTS IN CONDUCTORS AND SUPERCONDUCTORS IN SCHWARZSCHILD SPACE–TIME

International Journal of Modern Physics D ◽

10.1142/s021827180500678x ◽

2005 ◽

Vol 14 (05) ◽

pp. 817-835 ◽

Cited By ~ 1

Author(s):

B. J. AHMEDOV ◽

F. J. FATTOYEV

Keyword(s):

Magnetic Field ◽

Gravitational Field ◽

Neutron Stars ◽

Penetration Depth ◽

Skin Effect ◽

Outer Core ◽

Point Of View ◽

Time Dependent ◽

General Relativistic ◽

Stationary Gravitational Field

The general principles needed to compute the effect of a stationary gravitational field on the quasistationary electromagnetic phenomena in normal conductors and superconductors are formulated from general relativistic point of view. Generalization of the skin effect, that is the general relativistic modification of the penetration depth (of the time-dependent magnetic field in the conductor) due to its relativistic coupling to the gravitational field is obtained. The effect of the gravitational field on the penetration and coherence depths in superconductors is also studied. As an illustration of the foregoing general results, we discuss their application to superconducting systems in the outer core of neutron stars. The relevance of these effects to electrodynamics of magnetized neutron stars has been shown.

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Incommensurate Crystallization of Neutron Matter in Neutron Stars

East European Journal of Physics ◽

10.26565/2312-4334-2020-2-04 ◽

2020 ◽

Keyword(s):

Neutron Star ◽

Neutron Stars ◽

Specific Heat ◽

Inner Core ◽

Surface Region ◽

Outer Core ◽

Neutron Matter ◽

High Mass ◽

The Core ◽

Gravitational Stress

The composition of the neutron stars from its surface region, outer-core, inner-core, and to its center is still being investigated. One can only surmise on the properties of neutron stars from the spectroscopic data that may be available from time to time. A few models have suggested that the matter at the surface region of the neutron star is composed of atomic nuclei that get crushed under extremely large pressure and gravitational stress, and this leads to the creation of solid lattice with a sea of electrons, and perhaps some protons, flowing through the gaps between them. Nuclei with high mass numbers, such as ferrous, gold, platinum, uranium, may exist in the surface region or in the outer-core region. It is found that the structure of the neutron star changes very much as one goes from the surface to the core of the neutron star. The surface region is extremely hard and very smooth. Surface irregularities are hardly of the order of 5 mm, whereas the interior of the neutron star may be superfluid and composed of neutron-degenerate matter. However, the neutron star is highly compact crystalline systems, and in terrestrial materials under pressure, many examples of incommensurate phase transitions have been discovered. Consequently, the properties of incommensurate crystalline neutron star have been studied. The composition of the neutron stars in the super dense state remains uncertain in the core of the neutron star. One model describes the core as superfluid neutron-degenerate matter, mostly, composed of neutrons , and a small percentage of protons and electrons More exotic forms of matter are possible, including degenerate strange matter. It could also be incommensurate crystalline neutron matter that could be BCC or HCP. Using principles of quantum statistical mechanics, the specific heat and entropy of the incommensurate crystalline neutron star has been calculated assuming that the temperature of the star may vary between to . Two values for the temperature T that have been arbitrarily chosen for which the calculations have been done are and . The values of specific heat and entropy decrease as the temperature increases, and also, their magnitudes are very small. This is in line with the second law of thermodynamics.

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Roton instabilities in the superfluid outer core of neutron stars

Physical Review C ◽

10.1103/physrevc.103.065803 ◽

2021 ◽

Vol 103 (6) ◽

Author(s):

J. A. Gil Granados ◽

A. Muñoz Mateo ◽

X. Viñas

Keyword(s):

Neutron Stars ◽

Outer Core

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The role of mass, equation of state, and superfluid reservoir in large pulsar glitches

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa149 ◽

2020 ◽

Vol 492 (4) ◽

pp. 4837-4846 ◽

Cited By ~ 6

Author(s):

A Montoli ◽

M Antonelli ◽

P M Pizzochero

Keyword(s):

Neutron Star ◽

Equation Of State ◽

Neutron Stars ◽

Small Region ◽

Outer Core ◽

Rotational Dynamics ◽

Internal Layers ◽

S Wave ◽

Average Activity

ABSTRACT Observations of pulsar glitches may provide insights on the internal physics of neutron stars and recent studies show how it is in principle possible to constrain pulsar masses with timing observations. The reliability of these estimates depends on the current uncertainties about the structure of neutron stars and on our ability to model the dynamics of the superfluid neutrons in the internal layers. We assume a simplified model for the rotational dynamics of a neutron star and estimate an upper bound to the mass of 25 pulsars from their largest glitch and average activity: the aim is to understand to which extent the mass constraints are sensitive to the choice of the unknown structural properties of neutron stars, like the extension of the superfluid region and the equation of state. Reasonable values, within the range measured for neutron star masses, are obtained only if the superfluid domain extends for at least a small region inside the outer core, which is compatible with calculations of the neutron S-wave pairing gap. Moreover, the mass constraints stabilize when the superfluid domain extends to densities over nuclear saturation, irrespective of the equation of state tested.

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