Wind braking of magnetars H. Tong ( 仝号 ) Xinjiang Astronomical Observatory, Chinese Academy of Sciences Collaborators: J.P. Yuan (XAO), R.X. Xu (PKU), W. Wang (NAOC) For QCS Homepage:

Neutron star, pulsar and magnetar Neutron star=a star made of neutrons (NO!) Pulsar=rotating magnetized neutron star Magnetar: a special king of pulsars (powered by magnetic energy) – Anomalous X-ray pulsar (AXP) – Soft gamma-ray repeater (SGR)

Crab Magnetars my favriate!

Timing events of magnetars Basics: large P and Pdot 1.Varying period derivatives 2.Low magnetic field magnetar (small Pdot) 3.Anti-glitch 4.Negative correlation between Lx and Pdot NOT including glitches of magnetars, See Lu Jiguang's talk

Woods bursts A period of enhanced spindown

Varying spindown rate PSR J (Levin+ 2012)

Decreasing period derivative of the second low-B magnetar Tong & Xu 2013 RAA Scholz Decreasing spindown rate

Spindown behavior of the Galactic center magnetar, Kaspi Decreasing Lx 2. Increasing spindown rate negative correlation between Lx and Pdot

Anti-glitch of magnetar 1E ● Archibald+ (2013), Nature Anti-glitch 14 days interval

Open questions 1.How magnetars are spun down? Why so many timing events in and only in magnetars? Unified spindown mechanism of pulsars and magnetars My answer: wind braking (Tong et al. 2013, ApJ, 768, 144)

Traditional magnetar model (Mereghetti 2008) Magnetar = 1.young NS (SNR & MSC) 2.B dip > B QED =4.4×10 13 G (braking) 3.B mul = G (burst and super-Eddington luminosity and persistent emission)

Various alternatives (Tong & Xu 2014) 1. NS+twisted magnetosphere (Thompson et al. 2002; Beloborodov 2009) 2. Wind braking of magnetars (Tong et al. 2013) 3. Coupled magnetic and thermal evolution (Vigano+2013) 4. Fallback disk model (Alpar 2001) 5. Accretion induced star quake model (Xu et al. 2006) 6. Quark nova remnant (Ouyed et al. 2007) 7. Accreting WD model (Paczynski 1990)

General pictures of wind braking 1.Pulsars have a magnetosphere, where there is particle acceleration and subseuqent radiation process--> pulse profile 2.When flowing out, this particle compoent will also take away the rotational energy of the pulsar --> spindown Diple radiation+particle component: wind braking model (Xu & Qiao 2001, for normal pulsars)

Various winds 1. Solar wind 2. Steller wind: Wolf-Rayet star -->Ib,Ic SNe; HMXBs (wind accreting NSs) 3. Wind of pulsars and magnetars

The solar wind which we can feel its existence

Magnetic dipole braking of pulsars Rotating (perpendicular) dipole in vaccum! Only as first order approximation to the real case (Goldreich & Julian 1969, Ruderman & Sutherland 1975) It is only a pedagogical model!

wind braking of normal pulsars Rotational energy: magnetic dipole radiation+particle wind (rotation-powered) Effects: higher order modifications, e.g. braking index (Xu & Qiao 2001; Contopoulos & Spitkovsky 2006; Wang+ 2012) timing noise (Lyne+ 2010; Liu+ 2011) a rotation-powered PWN Exist: intermittent pulsars (Kramer+ 2006; Li, Tong )

Typical pulsar-SNR system (Gaensler & Slane 2006)

Intermittent pulsars B (Kramer+ 2006)

Wind braking of magnetars (Tong+ 2013) In summary Magnetism-powered particle wind When L p >> E dot, a much lower magnetic field (plus higher order effects, magnetar case)

Summary of wind braking of magnetars 1. Wind braking: Wind-aided spin down A lower surface dipole field Magnetars=NS+strong multipole field 2. Explain challenging observations of magnetars a)Their SNe energies are of normal value b)Non-detection of magnetars by Fermi-LAT c)The problem of low-B SGRs d)The relation between magnetars and HBPSRs e)A decreasing Pdot during magnetar outburst 3. Low luminosity mangetars more likely to have radio emissons 4. Two predictions – A magentism-powered PWN – A braking index n<3

SGR : long term flux evolution (Rea+ 2013)

Tong & Xu 2012 ApJ Low B magnetar due to a small inclination angle

Swift J : long term flux evolution (Scholz+ 2014)

Decreasing period derivative of the second low-B magnetar Tong & Xu 2013 RAA Scholz Decreasing Pdot a decresing particle wind

Spindown behavior of the Galactic center magnetar, Kaspi Decreasing Lx 2. Increasing spindown rate negative correlation between Lx and Pdot

Changes of polar cap opensing angle, Tong arXiv:

Anti-glitch of magnetar 1E ● Archibald+ (2013), Nature Anti-glitch 14 days interval

Modeling anti-glitch 1.Lyutikov (arXiv: ): corona-mass- eruption-like model 2.Tong ( ): wind braking 3.Katz ( ): retrograde accretion 4.Ouyed+ ( ): retrograde accreting quark-nova remnant 5.Huang+ ( ): collision by a small body Model 1& 2 are in the magnetar domain

Anti-glitch in the wind braking scenario Tong 2014 ApJ 1.Due to an enhanced particle wind 2.Anti-glitch always accompanied by radiative events 3.No anti-glitch, but a period of enhanced spindown ● Future anti-gltich without radiative event or a very small timescale can rule out the wind braking model

Woods bursts A period of enhanced spindown

If … Anti-glitch: due to a stronger particle wind ? ? ? ? ? ?: a weaker particle wind/the particle wind disappeared Spindown behavior of intermittent pulsars Li, Tong ApJ

Conclusions: Braking mechanism of pulsars and magnetars Magnetic dipole braking: perpendicular rotator in vacuum; must be wrong; correct to the 1 st order approximation (1969); only a pedagogical model 1. Wind braking of pulsars: 2 nd order effect (braking index, timing variations & noise); 1 st order effect seen in intermittent pulsars 2. Wind braking of magnetars: Pdot variation during the persistent state (several times); Pdot variation during the outburst (up to 100 times); Correlations between the timing and radiative events (low- B magnetars, anti-glitch etc)

If magnetars do not exist at all NS+twisted magnetosphere (Thompson et al. 2002; Beloborodov 2009) 2. Wind braking of magnetars (Tong et al. 2013) 3. Coupled magnetic and thermal evolution (Vigano+2013) 4. Fallback disk model (Alpar 2001) 5. Accretion induced star quake model (Xu et al. 2006) 6. Quark nova remnant (Ouyed et al. 2007) 7. Accreting WD model (Paczynski 1990) AXPs and SGRs must be quark star+fallback disk systems (Tong & Xu 2011,arXiv: ) See R. X. Xu's talk