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Magnetars: wind braking

H. Tong Xinjiang Astronomical Observatory. Magnetars: wind braking. PAC2012, Xiangshan. Where are they?. Traditional magnetar model . Magnetar = young NS (SNR & MSC) B dip > B QED =4.4×10 13 G ( braking )

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Magnetars: wind braking

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  1. H. Tong Xinjiang Astronomical Observatory Magnetars: wind braking PAC2012, Xiangshan

  2. Where are they?

  3. Traditional magnetar model • Magnetar = • young NS (SNR & MSC) • Bdip> BQED=4.4×1013 G (braking) • Bmul=1014 -1015 G (burst and super-Eddington luminosity and persistent emission)

  4. “Magnetic dipole braking” of normal pulsars • Rotational energymagnetic dipole radiation+particle wind (rotation-powered) • Effects: higher order modifications, e.g. braking index (Michel 1969; Manchester 1985; Xu & Qiao 2001; Contopoulos & Spitkovsky 2006; Wang+ 2012)timing noise (Lyne+ 2010; Liu+ 2011)+a rotation-powered PWN • Exist: intermittent pulsars (Kramer+ 2006; Camilo+ 2012)

  5. Intermittent pulsars B1931+24 (Kramer+ 2006)

  6. Magnetic dipole braking is only a pedagogical model! • Rotating dipole in vaccum! • Only as first order approximation to the real case • Normal pulsars braked down by a rotation-poweredparticle wind

  7. Existence of a particle wind in magnetars • Varying period derivative • Higher level of timing noise (compared with HBPSRs) • Magnetism-powered PWN • Correlation between Lpwn and Lx • Higher Lpwn/Edot

  8. PSR J1622-4950 (Levin+ 2012)

  9. Rotational energy loss rate • In summary • Magnetism-poweredparticle wind • When Lp >> Edot, a much lower magnetic field (plus higher order effects, magnetar case)

  10. Dipole magnetic field (1): magnetic dipole braking Polar magnetic field

  11. Dipole magnetic field (2): wind braking Dipole magnetic field in the case of wind braking

  12. Dipole B (case I)

  13. Conclusions (1) • Wind braking: • Wind-aided spin down • A lower surface dipole field • Magnetars=NS+strong multipole field • Explain challenging observations of magnetars • Their SNe energies are of normal value • Non-detection of magnetars by Fermi-LAT • The problem of low-B SGRs • The relation between magnetars and HBPSRs • A decreasing Pdot during magnetar outburst • Low luminosity mangetars more likely to have radio emissons • Two predictions • A magentism-powered PWN • A braking index n<3

  14. Conclusions (2): subsequent developments • Magnetism-powered pulsar wind nebula around SGR Swift J1834.9-0846 (Younes et al. 2012) • Geometrical effect during wind braking:small inclination angle--> higher B(Tong & Xu 2012)

  15. A paradigm shift in the future? • FAST: more radio-loud magnetars, HBPSRs, intermittent pulsars … • “Pulsars are electromagnetic braking” For short Pulsars are wind braking

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