Role of Landau quantization on the neutron-drip transition in magnetar crusts

Chamel, Nicolas; Stoyanov, Zh. K.; Mihailov, L.M.; Mutafchieva, Y. D.; Pavlov, R. L.; Velchev, Ch. J.

doi:10.1103/physrevc.91.065801

Cited by 53 publications

(81 citation statements)

References 37 publications

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“…Both models give similar quality fits to the data. Chamel et al [26] obtained qualitatively similar results using Hartree-Fock-Bogoliubov models. At a given n the equilibrium nucleus minimizes the total energy density of the system.…”

Section: Crust Compositionsupporting

confidence: 70%

Magnetar giant flare oscillations and the nuclear symmetry energy

2014

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*If the observed quasi-periodic oscillations in magnetar flares are partially confined to the crust, then the oscillation frequencies are unique probes of the nuclear physics of the neutron star crust. We study crustal oscillations in magnetars including corrections for a finite Alfvén velocity. Our crust model uses a new nuclear mass formula that predicts nuclear masses with an accuracy very close to that of the Finite Range Droplet Model. This mass model for equilibrium nuclei also includes shell corrections and an updated neutron-drip line. We perturb our crust model to predict axial crust modes and assign them to observed giant flare quasiperiodic oscillation frequencies from SGR 1806-20. We find magnetar crusts that match observations for various magnetic field strengths, entrainment of the free neutron gas in the inner crust, and crust-core transition densities. We find that observations can be reconciled with smaller values of the symmetry energy slope parameter, L, if there is a significant amount of entrainment of the neutrons by the superfluid or if the crust-core transition density is large. We also find neutron star masses and radii which are in agreement with expectations from what is known about low-density matter from nuclear experiment. Matching observations with a field-free model we obtain the approximate values of M = 1.35 M and R = 11.9 km. Matching observations using a model with the surface dipole field of SGR 1806-20 (B = 2.4 × 10 15 G) we obtain the approximate values of M = 1.25 M and R = 12.4 km.

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Section: Crust Compositionsupporting

confidence: 70%

Magnetar giant flare oscillations and the nuclear symmetry energy

2014

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“…However, in Refs. [32,33], the non-negligible effect of the magnetic field on the properties of the outer crust has already been discussed. Even though the largest fields detected on the surface of magnetars are 2 × 10 15 G on the SGR 180620 (see, e.g., Ref.…”

Section: Discussionmentioning

confidence: 99%

“…[32], within a Hartree-Fock-Bogoliubov calculation, and it was shown that the Landau quantization of the electron motion could affect the outer crust equation of state, giving rise to more massive outer crusts than the expected in usual neutron stars. Also, the neutron drip density and pressure are affected by a strong magnetic field, showing typical quantum oscillations, which shift the transition outer-inner crust to larger or smaller densities [33], according to the field intensity. The present work aims to study the effect of the magnetic field on the crust-core transition and completes the one in Ref.…”

Section: Introductionmentioning

confidence: 99%

Effect of strong magnetic fields on the crust-core transition and inner crust of neutron stars

et al. 2017

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The Vlasov equation is used to determine the dispersion relation for the eigenmodes of magnetized nuclear and neutral stellar matter, taking into account the anomalous magnetic moment of nucleons. The formalism is applied to the determination of the dynamical spinodal section, a quantity that gives a good estimation of the crust-core transition in neutron stars. We study the effect of strong magnetic fields, of the order of 10 15 -10 17 G, on the extension of the crust of magnetized neutron stars. The dynamical instability region of neutron-proton-electron (npe) matter at subsaturation densities is determined within a relativistic mean-field model. It is shown that a strong magnetic field has a large effect on the instability region, defining the crust-core transition as a succession of stable and unstable regions due to the opening of new Landau levels. The effect of the anomalous magnetic moment is non-negligible for fields larger than 10 15 G. The complexity of the crust at the transition to the core and the increase of the crust thickness may have direct impact on the properties of neutrons stars related with the crust.

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“…For more details on the effects on the magnetic field on the neutron-drip transition point, we address the reader to Refs. [22,23]. In these works, where the magnetic-field effect on nuclei was neglected, it was found that P drip increases linearly with extreme magnetic fields (B 10 16 G).…”

Section: The Neutron-drip Transition Pointmentioning

confidence: 99%

“…Thus the outer crust is the result of a competition between the electronic energy, favoring neutron-rich nuclei, and the nuclear symmetry energy, favoring fairly symmetric nuclei. The outer crust ends when the nuclei become unstable against neutron emission because of their high neutron imbalance, becoming the inner crust where a free neutron gas is also present [22,23]. The ideal boundary between the two crusts is called neutron-drip transition, and the related dripping pressure P drip plays a fundamental part in order to calculate the outer-crust spatial extension [24,25].…”

Section: Introductionmentioning

confidence: 99%

Outer crust of a cold non-accreting magnetar

et al. 2015

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The outer-crust structure and composition of a cold, non-accreting magnetar are studied. We model the outer crust to be made of fully equilibrated matter where ionized nuclei form a Coulomb crystal embedded in an electron gas. The main effects of the strong magnetic field are those of quantizing the electron motion in Landau levels and of modifying the nuclear single-particle levels producing, on average, an increased binding of nucleons in nuclei present in the Coulomb lattice. The effect of a homogeneous and constant magnetic field on nuclear masses has been predicted by using a covariant density functional in which induced currents and axial deformation due to the presence of a magnetic field that breaks time-reversal symmetry have been included self-consistently in the nucleon and meson equations of motion.Although not yet observed, for B 10 16 G both effects contribute to produce different compositions-odd-mass nuclei are frequently predicted-and to increase the neutron-drip pressure as compared to a typical neutron star. Specifically, in such a regime, the magnetic-field effects on nuclei favor the appearance of heavier nuclei at low pressures. As B increases, such heavier nuclei are also preferred up to larger pressures. For the most extreme magnetic field considered, B = 10 18 G, and for the models studied, almost the whole outer crust is made of 92 40 Zr 52 .

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Role of Landau quantization on the neutron-drip transition in magnetar crusts

Cited by 53 publications

References 37 publications

Magnetar giant flare oscillations and the nuclear symmetry energy

Magnetar giant flare oscillations and the nuclear symmetry energy

Effect of strong magnetic fields on the crust-core transition and inner crust of neutron stars

Outer crust of a cold non-accreting magnetar

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