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Low-magnetic-field magnetars

Low-magnetic-field magnetars. Roberto Turolla Paolo Esposito. Reporter: Fu, Lei ArXiv:1303.6052 20130506. Alternative senarios. ABCs of magnetars. Low-magnetic-field magnetars. Interpretation in the Standard model. Contents. ABCs of magnetars. Discovery of magnetars

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Low-magnetic-field magnetars

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  1. Low-magnetic-field magnetars Roberto Turolla Paolo Esposito Reporter: Fu, Lei ArXiv:1303.6052 20130506

  2. Alternative senarios ABCs of magnetars Low-magnetic-field magnetars Interpretation in the Standard model Contents

  3. ABCs of magnetars • Discovery of magnetars • SGR(Soft Gamma repeater) • 1979.01.07-----0.25s burst from SGR 1806-20 detected • 1979.03.05-----first giant flare from SGR 0526-66 • AXP( Anomalous X-ray pulsars) • 1981---- 1E 2259+586 at the center of CTB 109 • SGR like burst was observed in 1E 2259+586, 1E 1048.1-5937 and 1E 1547-5408

  4. short bursts

  5. intermediate flares

  6. Giant flares

  7. ABCs of magnetars • Definition • a source powered by magnetic energy • variable persistent • short X/γ-ray bursts above criteria • High-B radio pulsars(HBPSRs), X-ray dim isolated neutron stars(XDINSs) • Low B magnetars

  8. Low B magnetars • SGR 0418+5729 • bursts on 2009.06.05 • persistent luminosity • spin period • period derivative • derived magnetic field • characteristic age~ 36Myr

  9. SGR 0418+5729

  10. Low B magnetars • Swift J1822.3-1606 • bursts on 2011.07.14 • 1993.09.14-15(ROSAT) • spin period • period derivative • derived magnetic field • characteristic age~ 0.8Myr

  11. Swift J1822.3-1606

  12. Interpretation in the Standard mdel • Origin of persistent emission and bursts • internal heating by magnetic field decay • Hall drift and ohmic dissipation • Ambipolar diffusion not important in superfluid core • other heating sources • twisted magnetosphere caused by the motions of star interior • small and large scale fractures in the crust

  13. Interpretation in the Standard mdel • Old magnetars • small number of bursts and comparatively low energetics • internal toroidal component decay • field decay timescale

  14. Interpretation in the Standard mdel • Numerical approach • surface magnetic field • different internal toroid component • considering only the ohmic diffusion due to numerical difficulties in treating the Hall term

  15. SGR 0418+5729

  16. Swift J1822.3-1606

  17. Outburst decay

  18. Alternative senarios • No direct measure of the surface magnetic field of magnetars • cyclotron energy of electron ~MeV • proton line • Alternative model • fossil-disc left in supernova explosion or after a CE phase • SGR 0418+5729 • initial spin period >70 ms • reach current period in • burst?

  19. Alternative senarios • Massive white dwarf (1.3-1.4 solar mass)with high magnetic field • the inertia of WD • Rotational energy losses can be • dipole magnetic field • burst activity is powered by the relief of mechanical stresses as the WD spin down(gravity overcoming centrifugal forces) • the energy release is • In order to explain the giant flare • fast spin period < 5s ? • recent calculation shows the minimum period of WD~0.3s

  20. Alternative senarios • Quark stars • degenerate debris shell co-rotating with the star or confined in a Keplerian ring • the magnetic field can reach due to the color ferromagnetism in the quark matter • spin down by magnetic braking and expels from superfluid/conducting magnetic vortices

  21. Alternative senarios • X-ray emission is powered by • magnetic decreases and reconnections • accretion of the degenerate material • Bursts is due to clumps accretion • SGR 0418-5729 • an evolved quark-ring system • characteristic age(n=4) • the magnetic field is evolve from

  22. Conclusion • The discovery of low-B magnetar has opened new perspectives in NS astrophysics • SGR 0418+5729 and Swift J1822.3-1606 are likely to be old magnetars with strong internal toroidal field • 20% of Galactic radio pulsars have a dipole field higher than SGR 0418+5729 may show up as a transient magnetar

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