Electrical conductivity of the neutron star crust at low temperatures

Chugunov, A. I.

doi:10.1134/s1063773712010021

Cited by 19 publications

(21 citation statements)

References 27 publications

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“…This implied that at T < T U the conductivity would be in practice determined by impurities and structure defects of the lattice, rather than by the electron-phonon scattering . However, Chugunov (2012) showed that distortion of electron wave functions due to interaction with the Coulomb lattice destroys this picture and strongly slows down the increase of the conductivity. As a result, the conductivities in neutron star envelopes can be treated neglecting the "freezing-out" of the Umklapp processes.…”

Section: A21 Electron-ion Scatteringmentioning

confidence: 99%

Neutron Stars—Cooling and Transport

2015

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Observations of thermal radiation from neutron stars can potentially provide information about the states of supranuclear matter in the interiors of these stars with the aid of the theory of neutron-star thermal evolution. We review the basics of this theory for isolated neutron stars with strong magnetic fields, including most relevant thermodynamic and kinetic properties in the stellar core, crust, and blanketing envelopes.

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Section: A21 Electron-ion Scatteringmentioning

confidence: 99%

Neutron Stars—Cooling and Transport

2015

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“…While these assumptions make the numerical computation feasible, further processes may affect the formation of magnetic spots. In principle, the magnetic field evolution is coupled to its thermal evolution, as conductivity is a function of temperature (Chugunov 2012). Moreover, thermoelectric effects can in principle increase the magnetic field and consequently enhance its strength in regions where high temperature gradients appear (Urpin & Yakovlev 1980;Geppert 2017).…”

Section: Discussionmentioning

confidence: 99%

Magnetic Axis Drift and Magnetic Spot Formation in Neutron Stars with Toroidal Fields

Gourgouliatos

Hollerbach

2017

ApJ

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We explore magnetic field configurations that lead to the formation of magnetic spots on the surface of neutron stars, and to the displacement of the magnetic dipole axis. We find that a toroidally dominated magnetic field is essential for the generation of a single spot with a strong magnetic field. Once a spot forms, it survives for several million years, even after the total magnetic field has decayed significantly. We find that the dipole axis is not stationary with respect to the neutron star's surface and does not in general coincide with the location of the magnetic spot. This is due to non-axisymmetric instabilities of the toroidal field that displace the poloidal dipole axis at rates that may reach 0.4 • per century. A misaligned poloidal dipole axis with the toroidal field leads to more significant displacement of the dipole axis than the fully aligned case. Finally we discuss the evolution of neutron stars with such magnetic fields on the P− Ṗ diagram and the observational implications. We find that neutron stars spend a very short time before they cross the Death-Line of the P − Ṗ diagram, compared to their characteristic ages. Moreover, the maximum intensity of their surface magnetic field is substantially higher than the dipole component of the field. We argue that SGR 0418+5729 could be an example of this type of behaviour, having a weak dipole field, yet hosting a magnetic spot responsible for its magnetar behaviour. The evolution on the pulse profile and braking index of the Crab pulsar, which are attributed to an increase of its obliquity, are compatible with the anticipated drift of the magnetic axis.

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“…We used a numerical model that incorporates state-of-the-art microphysics involving the electrical conductivity at the neutron star crust (Potekhin 1999;Chugunov 2012) and consistent thermal evolution profiles (Aguilera et al 2008). Our treatment took into account diffusion of the currents in the neutron star crust and advection of the field as a direct consequence of the matter accretion onto the surface.…”

Section: Discussionmentioning

confidence: 99%

“…In the NS crust, the principal charge carriers are the electrons, and thus the transport coefficient, σ, is determined taking into account every electron scattering-on processes: ions (p), phonons (ph), and impurities (Q). We used the non-quantizing electron conductivity from a public code 1 based on Potekhin (1999), with the modifications introduced by Chugunov (2012). These routines give σ as a function of the temperature, T , density, ρ, magnetic field, B, atomic and mass numbers, (Z, A), auxiliary mass number, which incorporates the free neutron gas, A * , and the impurity content parameter, Q = Z 2 imp .…”

Section: Magnetic Field Evolutionmentioning

confidence: 99%

Exploring jet-launching conditions for supergiant fast X-ray transients

García

Aguilera

Romero

2014

A&A

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Context. In the magneto-centrifugal mechanism for jet formation, accreting neutron stars are assumed to produce relativistic jets only if their surface magnetic field is weak enough (B ∼ 10 8 G). However, the most common manifestation of neutron stars are pulsars, whose magnetic field distribution peaks at B ∼ 10 12 G. If the neutron star magnetic field has at least this strength at birth, it must decay considerably before jets can be launched in binary systems. Aims. We study the magnetic field evolution of a neutron star that accretes matter from the wind of a high-mass stellar companion so that we can constrain the accretion rate and the impurities in the crust, which are necessary conditions for jet formation. Methods. We solved the induction equation for the diffusion and convection of the neutron star magnetic field confined to the crust, assuming spherical accretion in a simpliflied one-dimensional treatment. We incorporated state-of-the-art microphysics, including consistent thermal evolution profiles, and assumed two different neutron star cooling scenarios based on the superfluidity conditions at the core. Results. We find that in this scenario, magnetic field decay at long timescales is governed mainly by the accretion rate, while the impurity content and thermal evolution of the neutron star play a secondary role. For accretion ratesṀ > ∼ 10 −10 M yr −1 , surface magnetic fields can decay up to four orders of magnitude in ∼10 7 yr, which is the timescale imposed by the evolution of the high-mass stellar companion in these systems. Based on these results, we discuss the possibility of transient jet-launching in strong windaccreting high-mass binary systems like supergiant fast X-ray transients.

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Electrical conductivity of the neutron star crust at low temperatures

Cited by 19 publications

References 27 publications

Neutron Stars—Cooling and Transport

Neutron Stars—Cooling and Transport

Magnetic Axis Drift and Magnetic Spot Formation in Neutron Stars with Toroidal Fields

Exploring jet-launching conditions for supergiant fast X-ray transients

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