Multiband observation and theory of magnetars

H. Tong (仝号 )Xinjiang Astronomical Observatory, CAS

2013.8

For 2013 Pulsar summer school @Beijing

Contents Introduction Radio observations of magnetars Soft X-ray observations of magnetars Optical/IR/HX/gamma observations Magnetar/PWN/SNR system Summary

Where are they?

What's AXPs & SGRs

AXPs: anomalous X-ray pulsarsLx>Edot (not necessary!) No binary signature

SGRs: soft gamma-ray repeatersSoft: typical photon energy is lowerRepeater: recurrent bursts

The same class!

Critical magnetic field

Cyclotron energy = electron rest mass

Microscopic process: QED

Traditional magnetar model(2008)

Magnetar = 1. young NS (SNR & MSC)

2. B_dip> B_QED=4.4*10^13 G (braking)3. B_mul=10^14-10^15 G (burst and

super-Eddington luminosity and persistent emission)

prehistory of magnetars

1932: Chadwick, discovery of neuton

1932: Landau, celestial objects with nuclear density

1934: Baade & Zwicky, NSs born in SNe

1939: Oppenheimer & Volkoff, NS structure M_sun, 10 km

1967: Hewish & Bell, discovery of (rotation- powered) pulsars

1971: Giacconi et al., discovery of accretion- powered X-ray pulsars

A brief history of magnetars

1979: giant flare of SGR 0526-661981: anomalous X-ray pulsars1992: “magnetars”1998: Timing of SGR 1806-20giant flare of SGR 1900+14

2006-: multiwave era (radio, IR, HX)2010: “low magnetic field” magnetar (B<7.5*10^12 G)

The magnetar model

1. Duncan & Thompson 1992: 1. Dynamo

2. spin-down

2. Usov 1992: millisecond magnetar as central engine for GRBs

3. Paczynski 1992: super-Eddington luminosity

1992: “magnetar”

Magnetar timing Kouveliotou et al. (1998)

SGR 1806-20: P=7.47s

Pdot= 8.24*10^-11

tau=1500 yr B=8*10^14. G (assuming magnetic dipole braking!)

Giant flare (Hurley et al. 1999)

1998: SGR 1900+14Modeling: Yu+ 2013

Other observations

Burst from one AXP 1E 1048.1-5937 (2002) Glitches during outburst of 1E 2259+586 (2003) Intermediate flare from 1E 1547.0-5408 (2009)

AXPs & SGRs belong to the same class!

Observations for the magnetar model (Tong & Xu 2011)

1. B from P and Pdot2. Cyclotron lines (?)3. Pulsating tail4. Super-Eddington luminosity5. SGR-like bursts from HBPSR6. ...(other more model dependent ones)

Failed predictions

1. SNe more energetic (2006)2. A larger kick velocity (2007)3. No radio emissions (2006)4. High-energy gamma-ray detectable by Fermi/LAT

(2010)5. B>BQED (2010)6. Always a large Lx (Lx>Edot):

transients & HBPSRs7. Precession

3+1 things to do

1. Origin of strong-B2. Emission mechanisms in the magnetar

domain

3. Alternative models of AXPs/SGRs

4. Relation between magnetars and other pulsar-like objects (XDINSs, CCOs, HBPSRs, and normal pulsars)

Various alternatives

1. NS+twisted magnetosphere (Thompson et al. 2002; Beloborodov+ 2007, 2009)

2. Wind braking of magnetars (Tong et al. 2013)3. Fallback disk model (Alpar 2001)4. Accretion induced star quake model (Xu et al. 2006)5. Quark nova remnant (Ouyed et al. 2007)6. Accreting WD model (Malheiro et al. 2011)

No radio emissions from magnetars?

No radio emissions from magnetars (QED calculations, Baring & Harding 1998)

Transient pulsed radio emssions from AXP XTE J1810-197 (Camilo et al. 2006)

Peculiarities (Mereghetti 2008): variable flux and pulse profileFlat spectraTransient in nature

Levin et al. 2010

Levin et al. 2012

“Fundamental plane” of magnetar radio emissions (Rea et al. 2012)

“Fundamental plane” of magnetar radio emissions (Rea+ 2012)

A magnetar is radio-loud if and only if:

Rotation-powered

Failed predictions Failed in one new source Swift J1834.9-0856

(Tong, Yuan & Liu 2013, RAA, 13, 835; obs 2012.5/6)

GBT nondetection (Esposito+ arXiv:1212.1079; obs 2011.8-11)

GMRT nondetection (obs: 2013.1)

Alternative idea of magnetar radio emissions

“Low luminosity magnetars are more likely to have radio emissions”

magnetism-powered

Interesting application

• VLBI measurement of magnetar kick velocity: Failed predictionsXTE J1810-197: Helfand+ 20071E 1547.0-5408: Deller+ 2012J1622-4950: ?

4th radio-loud magnetar at the Galatic Center: Rea et al. 2013

Espinoza et al. 2011:From normal pulsars to magnetars?

Relations with radio pulsars

Modeling: Liu+ 2012

Soft X-ray observations

Timing P & Pdot measurement (1998) Glitch (2000) Low-B magnetars (2010) Anti-glitch (2013)

Outbursts, transientRelations with other pulsar-like objects (XDINSs, CCOs etc)

Magnetar timing Kouveliotou et al. (1998)

SGR 1806-20: P=7.47s

Pdot= 8.24*10^-11

tau=1500 yr B=8*10^14. G (assuming magnetic dipole braking!)

Problems: 1. the existence of HBPSRs,2. the Pdot variations of magnetars, 3. Low-B magnetars (2010)!

Glitches in magnetars

Glitch in AXP 1E 2259+586 (Kaspi+ 2003)1.Large amplitude: 2.Accompanied by outburst3.Increase in spindown rate: 2 times larger

Outburst of 1E 2259+586Kaspi et al. (2003)

Summary of glitches in magnetars (Dib+ 2008)

1.Most AXPs show glitches2.Some (and only some) are associated with

radiative events3.Large recoveries (Q>1): superfluid of

magnetars rotates slower than the crust?

Low-B magnears: two sources (-2013.7)

1. SGR 0418+5729 (Rea+2010)2. Swift J1822.3-1606 (Rea+2012)

SGR 0418+5729 Bursts detected by Fermi-GBM, 2009/6/5 (van

der Horst et al. 2010) Early X-ray and optical obs:

Pdot<1.1*10^-13

Bdip<3*10^13 G (Esposito et al. 2010) One year obs: Pdot<6.0*10^-15 (P=9.1sec)Pdot<6.0*10^-15 (P=9.1sec) Bdip<7.5*10^12 G (Rea et al. 2010, Science)

Implications Assuming magnetic dipole braking: Bdip<7.5*10^12 G tau_c>2.4*10^7 yr Rotational energy: Edot<3.1*10^29 erg s^-1 X-ray luminosity: Lx=6.2*10^31 erg s^-1

Implications-IIAssuming B-powered: Bmul>5*10^14 G

Problems?

Magnetar = • young NS (SNR etc)• Bdip> 4.4*E13 G (braking)• Bmul=10^14-10^15 G (burst and

persistent emission and super-Eddington luminosity)

“Old magnetars” Turolla et al. (2011) Magnetars: strong internal toroidal field

Alternatives• Old magnetars (Turolla+2011)• Wind braking (Tong& Xu 2013)

• Disk spindown (Alpar+2011)

• Quark-Nova remnant (Ouyed+2011)

• White dwarf model (Malheiro+2012)

Wind braking of magnetars

Tong+2013, ApJ

Wind braking of SGR 0418+5729

Tong & Xu 2012, ApJL

Anti-glitch of magnetar 1E 2259+586

● Archibald+ (2013), Nature

Anti-glitch in SGR 1900+14

● Woods+ (1999)

Net spindown of PSR J1846-0258

● Livingstone+ (2010)Q=8.7

Modeling anti-glitch

1.Lyutikov (arXiv:1306.2264): corona-mass-eruption-like model

2.Tong (arXiv:1306.2445): wind braking3.Katz (arXiv:1307.0586): retrograde accretion4.Ouyed+ (arXiv:1307.1386): retrograde

accreting quark-nova

Wind braking

Particle wind luminosity:

Anti-glitch in the wind braking scenario

1.Due to an enhanced particle wind2.Anti-glitch always accompanied by radiative

events3.No anti-glitch, but an enhanced period of

spindown● Future anti-gltich without radiative event or a

very small timescale can rule out the wind braking model

Other observations

A debris disk around one AXP (Wang et al. 2006) QPOs (Israel et al. 2005): magnetar seismology“free oscillation of the central star”

Summary: multiband observations

transient radio emissions Soft X-ray activities (timing, radiative) Optical/IR: fallback disk (Wang+ 2006)

Hard X-ray: burst (& giant flares) & persistent Gamm-ray: nondetection by Fermi (Failed predictions) PWN/SNR: normal SNe energies (failed predictions) & possible PWN

Summary: Magnetars in astrophysics (Kaspi 2010)

1. AXP/SGR2. XDINSs: dead magnetar3. CCO: magnetar-in-waiting /disk braked down

magnetar4. HBPSR: magnetar activities also seen

(PSR J1846-0258)5. Low B SGR: magnetar activities in normal pulsars in

the future!6. Magnetars in binary system?

Thanks!

Failed predictions I: SNe energy

Vink & Kuiper (2006)

Possible solution

Spin-down time scale:

Wind braking of magnetars (Tong+ 2012): a dipole field 10 times lower

A high dipole field, magnetic dipole braking

Failed predictions II: kick velocity

Helfand et al. (2007) (VLBA)

VLBI obs of the second radio-loud magnetar: AXP 1E 1547.0-5408Deller et al. 2012

Proper motion of SGR 1806-20 and SGR 1900+14 through NIR astrometry(arXiv:1210.8151)

Failed predictions III: No radio emissions

No radio emissions from magnetars (QED calculations, Baring & Harding 1998)

Transient pulsed radio emssions from AXP XTE J1810-197 (Camilo et al. 2006)

Peculiarities (Mereghetti 2008): variable flux and pulse profileFlat spectraTransient in nature

“Fundamental plane” of magnetar radio emissions (Rea et al. 2012)

“Fundamental plane” of magnetar radio emissions

A magnetar is radio-loud if and only if:

Failed in one new source (Tong, Yuan & Liu 2013) “Low luminosity magnetars are more likely to have radio emissions”

Failed prediction IV: Fermi/LAT obs of 4U 0141+61

(Sasmaz Mus & Gogus 2010; Tong, Song, & Xu 2010)

Exposure: 31.7 Ms No detection!

Fermi/LAT observation of all magnetars

(Fermi-LAT collaboration 2010;Tong, Song, & Xu 2011)

Possible solutions

1. Accretion model for AXPs and SGRs2. Wind braking of magnetars:

a different magnetospheric structure

Failed predictions V: Low-B SGR

(Rea et al. 2010)

Problems of SGR 0418

1. B_mul>>B_dip?2. Burst-active at 10^6-10^7 yr?

Too many SGR in our Galaxy (Muno et al. 2008)3. What about XDINSs?

Another possibility (Tong & Xu 2012)

A normal magnetar Instead of a low-B magnetar

Failed predictions VI: A radio loud magnetar (Levin et al. 2010)

PSR J1622-4950 Discovered 2009/04 HRTU survey, Parkes Edot=8.5*10^33 erg s^-1 Lx=2.5*10^33 erg s^-1 (Chandra)

P-Pdot diagram

Why Lx so low?

Also transient magnetars, e.g., XTE J1810-197 and HBPSRsCorona model is not the full story!

Failed predictions: VIIfree precession of magnetars

Prolate in shape Free precession (Thompson et al. 2000):