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Journal ArticleDOI

Upper critical field and (non)-superconductivity of magnetars

04 Sep 2015-Physics of Particles and Nuclei (Pleiades Publishing)-Vol. 46, Iss: 5, pp 826-829
TL;DR: In this article, the authors construct equilibrium models of compact stars using a realistic equation of state and obtain the density range occupied by the proton superconductor in strong B-fields.
Abstract: We construct equilibrium models of compact stars using a realistic equation of state and obtain the density range occupied by the proton superconductor in strong B-fields. We do so by combining the density profiles of our models with microscopic calculations of proton pairing gaps and the critical unpairing field H c2 above which the proton type-II superconductivity is destroyed. We find that magnetars with interior homogeneous field within the range 0.1 ≤ B 16 ≤ 2, where B 16 = B/1016 G, are partially superconducting, whereas those with B 16 > 2 are void of superconductivity. We briefly discuss the neutrino emissivity and superfluid dynamics of magnetars in the light of their (non)-superconductivity.
Citations
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Journal ArticleDOI
TL;DR: In this article, the authors argue that collisions of dilute axion stars with neutron stars, of the type known as "magnetars," may be the origin of most of the observed fast radio bursts.
Abstract: Axions may make a significant contribution to the dark matter of the Universe. It has been suggested that these dark matter axions may condense into localized clumps, called “axion stars.” In this paper we argue that collisions of dilute axion stars with neutron stars, of the type known as “magnetars,” may be the origin of most of the observed fast radio bursts. This idea is a variation of an idea originally proposed by Iwazaki. However, instead of the surface effect of Iwazaki, we propose a perhaps stronger volume effect caused by the induced time dependent electric dipole moment of neutrons.

43 citations

Journal ArticleDOI
13 Oct 2020
TL;DR: In this article, a new equation of state for the baryonic matter under an intense magnetic field was constructed within the framework of covariant density functional theory, where the composition of matter includes hyperons as well as Δ-resonances.
Abstract: We construct a new equation of state for the baryonic matter under an intense magnetic field within the framework of covariant density functional theory. The composition of matter includes hyperons as well as Δ-resonances. The extension of the nucleonic functional to the hypernuclear sector is constrained by the experimental data on Λ and Ξ-hypernuclei. We find that the equation of state stiffens with the inclusion of the magnetic field, which increases the maximum mass of neutron star compared to the non-magnetic case. In addition, the strangeness fraction in the matter is enhanced. Several observables, like the Dirac effective mass, particle abundances, etc. show typical oscillatory behavior as a function of the magnetic field and/or density which is traced back to the occupation pattern of Landau levels.

21 citations

Journal ArticleDOI
TL;DR: In this article, a new equation of state for the baryonic matter under an intense magnetic field was constructed within the framework of covariant density functional theory, which includes hyperons as well as $ \Delta$-resonances.
Abstract: We construct a new equation of state for the baryonic matter under an intense magnetic field within the framework of covariant density functional theory. The composition of matter includes hyperons as well as $ \Delta$-resonances. The extension of the nucleonic functional to the hypernuclear sector is constrained by the experimental data on $\Lambda$ and $\Xi$-hypernuclei. We find that the equation of state stiffens with the inclusion of the magnetic field, which increases the maximum mass of neutron star compared to the non-magnetic case. In addition, the strangeness fraction in the matter is enhanced. Several observables, like the Dirac effective mass, particle abundances, etc show typical oscillatory behavior as a function of the magnetic field and/or density which is traced back to the occupation pattern of Landau levels.

17 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that the rapid crust-core coupling is incompatible with oscillation models of magnetars that completely decouple the core superfluid from the crust and that magnetar precession is damped by the coupling of normal fluids to the superfluid core and, if observed, needs to be forced or continuously excited by seismic activity.
Abstract: If a magnetar interior B -field exceeds 1015 G, it will unpair the proton superconductor in the stellar core by inducing diamagnetic currents that destroy the Cooper pair coherence. Then, the P -wave neutron superfluid in these non-superconducting regions will couple to the stellar plasma by scattering of protons off the quasiparticles that are confined in the cores of neutron vortices by the strong (nuclear) force. The dynamical timescales associated with this interaction span from several minutes at the crust-core interface to a few seconds in the deep core. We show that (a) the rapid crust-core coupling is incompatible with oscillation models of magnetars that completely decouple the core superfluid from the crust and (b) magnetar precession is damped by the coupling of normal fluids to the superfluid core and, if observed, needs to be forced or continuously excited by seismic activity.

13 citations

References
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Journal ArticleDOI
TL;DR: In this paper, an infinite series of particle-hole loops in S$-wave superfluid neutrinos were studied and the neutrino emission rate due to pair breaking was parametrically suppressed compared to its one-loop counterpart.
Abstract: Below the critical temperature of superfluid phase transition baryonic matter emits neutrinos by breaking and recombination of Cooper pairs formed in the condensate. The weak vector and axial-vector vertices and the neutrino loss rates via pair breaking are modified by strong interactions in nuclear medium. We study these modifications nonperturbatively by summing infinite series of particle-hole loops in $S$-wave superfluid neutron matter. The interactions in the particle-hole channel are described within the Landau Fermi-liquid framework with the Landau parameters derived from the microscopic theory. The $S$-wave superfluid is described within the BCS theory. We derive the renormalized three-point vector and axial-vector vertices and the complete polarization tensor of matter and its low momentum transfer expansion. The leading-order term in this expansion and the associated neutrino losses arise at $O({q}^{2})$, consistent with the $f$-sum rule. The neutrino emission rate due to the pair breaking is parametrically suppressed compared to its one-loop counterpart by the ratio of the neutron recoil energy to the temperature, which is of order $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$. The approximations to the normal and anomalous self-energies that guarantee the conformity of the theory with the generalized Ward identities are established.

47 citations

Journal ArticleDOI
TL;DR: In this article, the neutrino emissivities resulting from direct URCA processes in neutron stars were calculated in a relativistic Dirac-Hartree approach in presence of a magnetic field.
Abstract: The neutrino emissivities resulting from direct URCA processes in neutron stars are calculated in a relativistic Dirac-Hartree approach in presence of a magnetic field. In a quark or a hyperon matter environment, the emissivity due to nucleon direct URCA processes is suppressed relative to that from pure nuclear matter. In all the cases studied, the magnetic field enhances emissivity compared to the field-free cases.

46 citations

Journal ArticleDOI
TL;DR: In this article, the authors construct two-fluid equilibrium configurations for neutron stars with magnetic fields, using a self-consistent and non-linear numerical approach, and provide quantitative results for magnetic ellipticities of NSs, both in the normal- and superconducting-proton cases.
Abstract: We construct two-fluid equilibrium configurations for neutron stars (NSs) with magnetic fields, using a self-consistent and non-linear numerical approach. The two-fluid approach – likely to be valid for large regions of all but the youngest NSs – provides us with a straightforward way to introduce stratification and allows for more realistic models than the ubiquitous barotropic assumption. In all our models, the neutrons are modelled as a superfluid, whilst for the protons we consider two cases: one where they are a normal fluid and another where they form a type II superconductor. We consider a variety of field configurations in the normal-proton case and purely toroidal fields in the superconducting case. We find that stratification allows for a stronger toroidal component in mixed-field configurations, though the poloidal component remains the largest in all our models. We provide quantitative results for magnetic ellipticities of NSs, both in the normal- and superconducting-proton cases.

40 citations

Journal ArticleDOI
TL;DR: In this paper, the Paris nucleon-nucleon interaction was used as an input to study the superfluid 3 D 2 pairing instability in isospin-asymmetric nuclear matter.

34 citations

Journal Article
TL;DR: In this paper, the effect of the magnetic field on the energy loss rate in the direct Urca reactions is studied, and the general expres- sion for the neutrino emissivity at arbitrary magnetic field B is derived.
Abstract: The effect of the magnetic field on the energy loss rate in the direct Urca reactions is studied. The general expres- sion for the neutrino emissivity at arbitrary magnetic field B is derived. The main emphasis is laid on a case, in which the field is not superstrong, and charged reacting particles (e andp) pop- ulate many Landau levels. The magnetic field keeps the process operative if k=k Fn . N 2=3 Fp (N Fp is the number of the Lan- dau levels populated by protons and k k Fn k Fp k Fe ), that is beyond the well-known switch-on limit in the absence of the field, k< 0. Cooling of magnetized neutron stars with strong neutron superfluid in the outer cores and nonsuperfluid inner cores is simulated. The magnetic field near the stellar cen- ter speeds up the cooling if the stellar mass M is slightly less than the minimum massMc, at which the direct Urca reaction becomes allowed for B =0 .I fB =3 10 16 G, the affected mass range isMc M. 0:1Mc, while forB =3 10 15 G the range is Mc M. 0:015Mc. This may influence a theoreti- cal interpretation of the observed thermal radiation as illustrated for the Geminga pulsar. The case of superstrong magnetic fields (B & 10 18 G), such thate andp populate only the lowest Landau levels is briefly outlined.

30 citations