Effect of superfluidity on neutron star oscillations

Sotani, Hajime; Nakazato, Ken’ichiro; Iida, Kei; Oyamatsu, Kazuhiro

doi:10.1093/mnrasl/sls006

Cited by 80 publications

(98 citation statements)

References 46 publications

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“…A larger value of L tends to increase the nucleon number A, which leads to larger a; the charge number Z is almost unchanged, however, due to nuclear shell effects. Thus a larger value of L decreases the shear modulus and also the fundamental QPO frequency [9,10].…”

Section: A the Equation Of Statementioning

confidence: 97%

“…Following the proposal by Duncan [5], many have attempted to model the QPOs as torsional modes of the crust [e.g., [6][7][8]. If this is indeed the cause of the QPOs, then magnetars can give a unique insight into the microphysics of the neutron star crust [9], e.g., the nuclear symmetry energy S (n), here defined as the difference in energy between pure neutron matter and protonneutron symmetric matter as a function of the baryon density, n. In particular, crust frequencies are sensitive to the quantity L ≡ 3n 0 (∂S /∂n) n=n 0 [9,10]. In addition, different modes have different scalings with the neutron star mass and radius; it follows that observations of two or more modes, such as a fundamental and harmonic, can constrain the magnetar's mass and radius [8,11] and hence the equation of state (EOS) of dense matter.…”

Section: Introductionmentioning

confidence: 99%

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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: A the Equation Of Statementioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Magnetar giant flare oscillations and the nuclear symmetry energy

2014

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“…Such ignorance could modify L min . Now, we take into account the effect of neutron superfluidity on the shear torsional oscillations [65]. In general, it is considered that neutrons confined in the nuclei start to drip therefrom when the mass density becomes higher than ∼ 4 × 10 11 g cm −3 .…”

Section: Nuclei In Neutron Star Crusts and Nuclear Pastamentioning

confidence: 99%

Symmetry energy, unstable nuclei and neutron star crusts

Iida

Oyamatsu

2014

Eur. Phys. J. A

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Abstract. Phenomenological approach to inhomogeneous nuclear matter is useful to describe fundamental properties of atomic nuclei and neutron star crusts in terms of the equation of state of uniform nuclear matter. We review a series of researches that we have developed by following this approach. We start with more than 200 equations of state that are consistent with empirical masses and charge radii of stable nuclei and then apply them to describe matter radii and masses of unstable nuclei, proton elastic scattering and total reaction cross sections off unstable nuclei, and nuclei in neutron star crusts including nuclear pasta. We finally discuss the possibility of constraining the density dependence of the symmetry energy from experiments on unstable nuclei and even observations of quasi-periodic oscillations in giant flares of soft gamma-ray repeaters. PACS

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“…To theoretically explain these QPOs, there are many attempts in terms of the crustal torsional oscillations and/or the magnetic oscillations. In practice, one might be able to obtain the crust informations, if the observed QPO frequencies are considered as the results of the crustal torsional oscillations [5][6][7][8][9] . In addition to the QPOs discovered in the giant flares, another QPO frequency is recently discovered in the same soft-gamma repeater, i.e., SGR 1806−20 10 .…”

Section: Introductionmentioning

confidence: 99%

Identifications of quasi-periodic oscillations observed in soft-gamma repeaters with crustal torsional oscillations

Sotani

2017

The Fourteenth Marcel Grossmann Meeting

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The quasi-periodic oscillations discovered in soft-gamma repeaters are considered due to the phenomena strongly associated with the oscillations of central objects, i.e., the neutron star oscillations. In order to explain the frequencies of the observed quasiperiodic oscillations, we focus on the crustal torsional oscillations in neutron stars, where we also take into account the effect of electron screening. Then, we are successful to constrain the density dependence of the nuclear symmetry energy (L), identifying the observed frequencies as the crust torsional oscillations with various angular indices.

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Effect of superfluidity on neutron star oscillations

Cited by 80 publications

References 46 publications

Magnetar giant flare oscillations and the nuclear symmetry energy

Magnetar giant flare oscillations and the nuclear symmetry energy

Symmetry energy, unstable nuclei and neutron star crusts

Identifications of quasi-periodic oscillations observed in soft-gamma repeaters with crustal torsional oscillations

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