1S0 proton and neutron superfluidity in β-stable neutron star matter

Zuo, Wei; Li, Z.H.; Lu, Gendi; Li, J.Q.; Scheid, W.; Lombardo, U.; Schulze, H.-J.; Shen, Chen

doi:10.1016/j.physletb.2004.05.061

Cited by 52 publications

(36 citation statements)

References 42 publications

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“…where κ = π /mn is the quantum of circulation, a is the inter-vortex spacing and the neutron density is given by ρn = xnρ with the neutron fraction xn ≈ 0.9 − 0.95 (Zuo et al 2004). Given the logarithmic dependence on these parameters, we choose to expedite calculations and follow Andersson, Sidery & Comer (2007) and take a constant value for the quantity xn log (a/ξ) = 20 (note that a smaller value is considered by Link (2014)).…”

Section: Vortex Lengthmentioning

confidence: 99%

Mesoscopic pinning forces in neutron star crusts

Seveso¹,

Pizzochero²,

Grill³

et al. 2015

Mon. Not. R. Astron. Soc.

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The crust of a neutron star is thought to be comprised of a lattice of nuclei immersed in a sea of free electrons and neutrons. As the neutrons are superfluid their angular momentum is carried by an array of quantized vortices. These vortices can pin to the nuclear lattice and prevent the neutron superfluid from spinning down, allowing it to store angular momentum which can then be released catastrophically, giving rise to a pulsar glitch. A crucial ingredient for this model is the maximum pinning force that the lattice can exert on the vortices, as this allows us to estimate the angular momentum that can be exchanged during a glitch. In this paper we perform, for the first time, a detailed and quantitative calculation of the pinning force per unit length acting on a vortex immersed in the crust and resulting from the mesoscopic vortexlattice interaction. We consider realistic vortex tensions, allow for displacement of the nuclei and average over all possible orientation of the crystal with respect to the vortex. We find that, as expected, the mesoscopic pinning force becomes weaker for longer vortices and is generally much smaller than previous estimates, based on vortices aligned with the crystal. Nevertheless the forces we obtain still have maximum values of order f pin ≈ 10 15 dyn/cm, which would still allow for enough angular momentum to be stored in the crust to explain large Vela glitches, if part of the star is decoupled during the event.

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Section: Vortex Lengthmentioning

confidence: 99%

Mesoscopic pinning forces in neutron star crusts

Seveso¹,

Pizzochero²,

Grill³

et al. 2015

Mon. Not. R. Astron. Soc.

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“…There are many calculations of the 1S 0 neutron (nn) and proton (pp) gaps and there are some evaluations of 3P 2 neutron gaps; for references, see, e.g., Refs. [82][83][84][85][86][87][88]. Here, to be specific for the description of a superfluid phase in a neutron star, we use parametrizations of critical temperatures, T c , from Ref.…”

Section: Nucleon Pairingmentioning

confidence: 99%

Viscosity of neutron star matter andr-modes in rotating pulsars

Kolomeitsev

Voskresensky

2015

Phys. Rev. C

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We study viscosity of the neutron star matter and r-mode instability in rotating neutron stars. Contributions to the shear and bulk viscosities from various processes are calculated accounting for in-medium modifications of the nucleon-nucleon interaction. A softening of the pion mode at densities larger than the nuclear saturation density n 0 and a possibility of the pion condensation at densities above 3n 0 are included. The neutron-neutron and proton-proton pairings are incorporated where necessary. In the shear viscosity we include the lepton contribution calculated taking into account the Landau damping in the photon exchange, the nucleon contribution described by the medium-modified one-pion exchange, and some other terms, such as the novel phonon contribution in the 1S 0 superfluid neutron phase and the neutrino term in the neutrino opacity region. The nucleon shear viscosity depends on the density rather moderately and proves to be much less than the lepton term. On the contrary, among the terms contributing to the bulk viscosity, induced by the delay of the relaxation of lepton concentrations in the star matter perturbed by the r-modes, the term from the two-nucleon medium-modified Urca reactions possesses strongest density dependence (rising by several orders of magnitude for massive stars) because of the pion softening. Also, contributions to the bulk viscosity arising from other reactions induced by charged weak currents, e.g., in the Urca processes on a pion condensate and in direct Urca processes, are included. The radiative bulk viscosity induced by charged and neutral weak currents in the region of the neutrino transparency of the star is also calculated accounting for in-medium effects. We exploit the equation of state, which is similar to the Akmal-Pandharipande-Ravenhall equation of state up to 4n 0 , but is stiffer at higher densities, producing the maximum neutron star mass compatible with observations. The direct Urca processes do not appear up to 5n 0 (corresponding to the star mass M 1.9M ). Computed with account of in-medium effects, the frequency boundary of the r-mode stability for the stars with the mass 1.8M proves to be above the frequencies of all rotating young pulsars. However, none of the conventional contributions to the viscosity are able to explain the stability of rapid rotation of old recycled pulsars in x-ray binaries. To solve this problem we propose a novel efficient mechanism associated with the appearance of condensates of low-lying modes of bosonic excitations with finite momentum and/or with an enhancement of the inhomogeneous pion/kaon condensates in some parts of the star, if the angular velocity exceeds a critical value.

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“…The standard superfluid fraction, Q, is introduced to describe the protons and nuclei of the normal crust, I c = (1 − Q)I tot , and the neutron superfluid component, I s = QI tot , of the star. Although the neutron fraction varies with density, a typical average value is Q ≈ 0.95 (Zuo et al 2004). Regarding proton Figure 1.…”

Section: The Modelmentioning

confidence: 99%

Angular Momentum Transfer in Vela-Like Pulsar Glitches

Pizzochero

2011

ApJ

109

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The angular momentum transfer associated with Vela-like glitches has never been calculated directly within a realistic scenario for the storage and release of superfluid vorticity; therefore, the explanation of giant glitches in terms of vortices has not yet been tested against observations. We present the first physically reasonable model, both at the microscopic and macroscopic level (spherical geometry, n = 1 polytropic density profile, densitydependent pinning forces compatible with vortex rigidity), to determine where in the star the vorticity is pinned, how much of it is pinned, and for how long. For standard neutron star parameters (M = 1.4 M , R s = 10 km, Ω =Ω Vela = −10 −10 Hz s −1 ), we find that maximum pinning forces of order f m ≈ 10 15 dyn cm −1 can accumulate ΔL gl ≈ 10 40 erg s of superfluid angular momentum, and release it to the crust at intervals Δt gl ≈ 3 years. This estimate of ΔL gl is one order of magnitude smaller than that implied indirectly by current models for post-glitch recovery, where the core and inner-crust vortices are taken as physically disconnected; yet, it successfully yields the magnitudes observed in recent Vela glitches for both jump parameters, ΔΩ gl and ΔΩ gl , provided one assumes that only a small fraction (<10%) of the total star vorticity is coupled to the crust on the short timescale of a glitch. This is reasonable in our approach, where no layer of normal matter exists between the core and the inner-crust, as indicated by existing microscopic calculation. The new scenario presented here is nonetheless compatible with current post-glitch models.

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1S0 proton and neutron superfluidity in β-stable neutron star matter

Cited by 52 publications

References 42 publications

Mesoscopic pinning forces in neutron star crusts

Mesoscopic pinning forces in neutron star crusts

Viscosity of neutron star matter andr-modes in rotating pulsars

Angular Momentum Transfer in Vela-Like Pulsar Glitches

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