Flux tube clustering from magnetic coupling of adjacent type-I and -II superconductors in a neutron star: persistent gravitational radiation

Abstract

Adjacent type-I and -II proton superconductors in a rotation-powered pulsar are predicted to exist in a metastable state containing macroscopic and quantized flux tubes, respectively. Previous studies show that the type-I and -II regions are coupled magnetically, when macroscopic flux tubes divide dendritically into quantized flux tubes near the type-I-II interface, through a process known as flux branching. The studies assume that the normal-superconducting boundary is sharp, and the quantized flux tubes do not repel mutually. Here the sharp-interface approximation is refined by accounting for magnetic repulsion. It is found that flux tubes in the same flux tree cluster with a minimum-energy separation two to seven times less than that of isolated flux tubes. Neutron vortices pin and cluster about flux trees. We find that the maximum characteristic wave strain $h_0$ of the current quadrupole gravitational radiation emitted by a rectilinear array of clustered vortices exceeds by $(1+N_{\mathrm{v},\mathrm{t}}{)}^{1/2}$ the strain $h_0\sim 10^{-32}(f/30\mathrm{Hz}{)}^{5/2}(D/1\mathrm{kpc}{)}^{-1}$ emitted by uniformly distributed vortices, where $N_{\mathrm{v},\mathrm{t}}$ is the mean number of pinned vortices per flux tree, $f$ is the star's spin frequency, and $D$ is the star's distance from Earth. The factor $(1+N_{\mathrm{v},\mathrm{t}}{)}^{1/2}$ brings $h_0$ close to the sensitivity limit of the current generation of interferometric gravitational wave detectors under certain circumstances, specifically when flux branching forms relatively few (and hence relatively large) flux trees.

References in corpus (14)

• Type-1.5 Superconductors
• Searches for Continuous-Wave Gravitational Radiation
• Transitions between turbulent and laminar superfluid vorticity states in the outer core of a neutron star
• Searches for continuous gravitational waves from neutron stars: A twenty-year retrospective
• Magnetic Field Generation in Stars
• Flux tubes and the type-I/type-II transition in a superconductor coupled to a superfluid
• Type I and Two-Gap Superconductivity in Neutron Star Magnetism
• Stability of interlinked neutron vortex and proton flux tube arrays in a neutron star: equilibrium configurations
• Stability of interlinked neutron vortex and proton flux tube arrays in a neutron star. II. Far-from-equilibrium dynamics
• Continuous gravitational wave emission from neutron stars with pinned superfluids in the core
• Stability of interlinked neutron vortex and proton flux-tube arrays in a neutron star -- III. Proton feedback
• Probing Ensemble Properties of Vortex-avalanche Pulsar Glitches with a Stochastic Gravitational-Wave Background Search
• Persistent gravitational radiation from glitching pulsars. II. Updated scaling with vortex number
• Magnetic coupling through flux branching of adjacent type-I and -II superconductors in a neutron star