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Post-glitch relaxation in pulsars

Anthony van Eysden Andrew Melatos University of Melbourne. Post-glitch relaxation in pulsars. Outline. Motivation Modelling glitch recovery Fitting to radio timing data (what can we determine?). Motivation. Probe matter at (super) nuclear densities Strong nuclear force (QCD)

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Post-glitch relaxation in pulsars

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  1. Anthony van Eysden Andrew Melatos University of Melbourne Post-glitch relaxation in pulsars

  2. Outline • Motivation • Modelling glitch recovery • Fitting to radio timing data (what can we determine?)

  3. Motivation • Probe matter at (super) nuclear densities • Strong nuclear force (QCD) • Exotic states?

  4. Bulk nuclear matter at high density • `Best guess’ phase diagram for QCD • Transport coefficients phase dependent • No terrestrial experiments to test theory in super-dense/cold regime Alford et. al. RvMP (2008)

  5. Pulsar glitch recovery Two stages: • Sudden increase in frequency (<100s) • Recovery (~days) • Recovery typically parameterized by

  6. Modelling glitch recovery • Hydrodynamic (viscous fluid interior) • Relaxation of differential rotation between crust and fluid • No assumptions about the microphysics

  7. Ekman pumping • Angular momentum transferred in interior by convection, not diffusion

  8. The 1985 Vela glitch • Family of curves parameterized by crust fraction, • Time-scale is Ekman time, • Not exponential!

  9. A two component superfluid model • Now have two time-scales • Add mutual friction force Crust Viscosity , Viscous fluid (e.g. Proton-electron plasma) Mutual friction, Inviscid fluid (e.g. Neutron condensate)

  10. The 1985 Vela glitch • Can fit with two time scales • Fits improve as increases

  11. The 1975 Crab glitch • Naturally fits the overshoot in the Crab

  12. Comparison with nuclear theory Quark models Condensed proton/neutron models • Can discriminate between nuclear theories

  13. Future work • Fit to raw glitch data • Need more frequency vs time glitch recovery data! Data: Sarah Buchner, Hartebeesthoek observatory

  14. Things to include… • Magnetic fields • Superconductivity/flux-tubes • Turbulence • Stratification

  15. Conclusions • Can extract nuclear parameters and test nuclear models • Spin-up of a spherical container is not exponential • Constrain models by fitting to raw data

  16. Errors

  17. Three time-scale data (Vela 1988) • Fits data admirably • No degeneracy

  18. Nuclear puzzles • Ion collider experiments on nuclear compressibility hard or soft EoS? • Ion collider experiments on viscosity suggest near quantum minimum

  19. W W+dW Spin-up (Ekman pumping) • Formation of Boundary Layer • Three time scales • Induced Radial Flow - O(P) • Rotation Period (P) • Inflow to Boundary Layer • Ekman time - O(Re1/2 P) • Radial Inflow into Interior • Diffusion - O(Re P)

  20. Ekman pumping – terrestrial example • Ekman Time for teacup • Diffusion Time • Spin up time << Diffusion time • Spin down caused by bottom, not sides!! Spin Down of a Tea Cup

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