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Magnetars and White Dwarf Magnetars and White Dwarf PulsarsPulsars

Manuel Malheiro, Jorge Rueda, and Remo Ruffini Manuel Malheiro, Jorge Rueda, and Remo Ruffini Publ. Astron. Soc. Japan 64, Vol.3 (2012)

J. G. Coelho and M. Malheiro Publ. Astron. Soc. Japan 66 , Vol.1 (2014)

III Amazonian Symposium on Physics and V NRHEP Network Meeting:CELLEBRATING 100 YEARS OF

GENERAL RELATIVITYUFPA – 28/09 to 02/10/2015

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I – SGRs and AXPs : Unusual X-ray Neutron Star Pulsars.

VII – Conclusions.

II – Recent Observations: SGR 0418+5729, Massive and Highly Magnetized White Dwarf Pulsar.

IV – SGRs and AXPs as fast rotating-powered Magnetic White Dwarf Pulsars.

V – Outbursts mechanism: change of rotational energy from normal glitches (spin up events).

VI - Dipole magnetic moment of neutron stars and white dwarfs

III – Magnetar x White Dwarf Physical Scales.

Rotation-powered PulsarsNeutron Stars

N~1057 particles

M~1−2 Msol

R ~ 10-12 km B ~ 108 .... 13 G,

T ~ 106 .... 11 K

Spin fast - Periods (0.1 to 0.001) s

Spin down rate is small ~ 10-15 s/s

Efficiency =Lx /(dErot/dt) ~10-2 -10-1

~1015g/cm3}

Franco Pacini- Tommy Gold

Pulsars: magnetized rotating neutron stars

Kepler angular critical frequency Wk = (G M/R3) ½ ~ (G ) ½ ; W < Wk

Implies a maximum radius R3 < (G M/42) P 2

R < 1500 P 2/3 KmFastest pulsar = 716 rounds/s , period P = 1,4 mili seconds R < 18 KmMagnetars, minimum period P = 2 segundos, R < 2400 Km (White dwarf very dense)

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Neutron star spins very fast and emits a beam of electromagnetic radiation PULSAR

Crab Pulsar: P = 33 ms 30 rounds per second

Dipolar Magnetic Field

McGill Online Catalog of Magnetars McGill Online Catalog of Magnetars http://www.physics.mcgill.ca/~pulsar/magnetar/main.htmlhttp://www.physics.mcgill.ca/~pulsar/magnetar/main.html

Pulsars : neutron stars breaking by dipole radiation

Torque puramenteeletromagnético

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I -SGRs and AXPs: Unusual X-Ray Pulsars• Soft Gamma Repeaters (SGR) and Anomalus X-Ray Pulsars (AXP) are very slow rotating pulsars: long Periods P ~ (2 -11) s. Periods in a narrow range comparing to ordinary pulsars P ~ (0.001 – 1) s .

• Spin-down rates dP/dt ~ (10-13 – 10-10 ) s larger than normal pulsar (10-15 – 10-14 ) s .

• Isolated stars and only 26 confirmed comparing with more than 2000 pulsars known.

• Strong outburst of energies ~ (1041 - 1043) erg . SGRs, giant flares of even large energies ~ (1044 – 1047) erg.

• High X-ray luminosities Lx ~ (1032 – 1036) erg/s >> spin-

down rotational energy rate (seen as neutron star pulsars). • A reservoir of energy to explain the X-ray Luminosity : A reservoir of energy to explain the X-ray Luminosity :

ultra-strong magnetic fields in the interior and at the ultra-strong magnetic fields in the interior and at the surface of the star B ~ (10surface of the star B ~ (101414 -10 -101515) G .) G .

• MAGNETARS - Magnetic-powered X-Ray pulsars (seen MAGNETARS - Magnetic-powered X-Ray pulsars (seen as neutron stars).as neutron stars).

• Hot Stars – T ~ (0.4 – 0.6) KeV , larger than 10Hot Stars – T ~ (0.4 – 0.6) KeV , larger than 106 6 K.K.

• Young Stars – spin-down ages (10Young Stars – spin-down ages (1033-10-1055) yr ; except the ) yr ; except the new SGR 0418+5229 with 24 Myr. True ages??? new SGR 0418+5229 with 24 Myr. True ages???

SGRs • Recurrent sources of soft gamma ray burst, short times t ~ 0.1 s and Recurrent sources of soft gamma ray burst, short times t ~ 0.1 s and

Energy EEnergy E ~ 1041 erg/s . .• Occasionaly active episodes producing many short X-Ray bursts. Occasionaly active episodes producing many short X-Ray bursts.

lasting weeks or months, separated by quiescent phases of years or lasting weeks or months, separated by quiescent phases of years or decades.decades.

• Intermediate bursts t ~ 1 - 40 s, higher energy E ~ (10Intermediate bursts t ~ 1 - 40 s, higher energy E ~ (104141-10-104343) erg ) erg showing an Hard X-ray emission with E ~ 20 - 200 KeV .showing an Hard X-ray emission with E ~ 20 - 200 KeV .

• Extremely rare: giant flares E ~ (10Extremely rare: giant flares E ~ (104444-10-104747) erg (~ one at each 50 ) erg (~ one at each 50 ys). Initial spike t < 0.1 s (Hard X-ray) with a long tail t > 500 s. ys). Initial spike t < 0.1 s (Hard X-ray) with a long tail t > 500 s.

AXPsAXPs• Similar to SGR but weaker in intensity. No giant flares.Similar to SGR but weaker in intensity. No giant flares.• No recurrent gamma ray bursts.No recurrent gamma ray bursts.

McGill catalogue of SGRs&AXPsMcGill catalogue of SGRs&AXPs

http://www.physics.mcgill.ca/~pulsar/magnetar/main.htmlhttp://www.physics.mcgill.ca/~pulsar/magnetar/main.html

Recent review S. Meregheti, Astron. Astrophys. Rev. 15, 255 (2008) Recent review S. Meregheti, Astron. Astrophys. Rev. 15, 255 (2008)

Hard and soft Hard and soft short short Bursts of SGR 1806-20Bursts of SGR 1806-20

Two Two intermediateintermediate bursts of SGR 1900+14 bursts of SGR 1900+14

Three Three giant flares: giant flares: SGR 0526-66, SGR 1900+14, SGR 0526-66, SGR 1900+14, and SGR 1806-20and SGR 1806-20

From review of S. Meregheti, Astron. Astrophys. Rev. 15, 255 (2008)

Difficulties of Magnetar ModelDifficulties of Magnetar Model

• Inconclusive measurements of cyclotron resonance Inconclusive measurements of cyclotron resonance lines to estimate the magnetic field strength. lines to estimate the magnetic field strength.

• No high-energy gamma emission of Magnetars No high-energy gamma emission of Magnetars found recently by Fermi sattelite.found recently by Fermi sattelite.

• Not viable to relate magnetars to the energy of Not viable to relate magnetars to the energy of supernova remnants, to formation of Black Holes supernova remnants, to formation of Black Holes or to Gamma Ray Burst (controversial).or to Gamma Ray Burst (controversial).

• Very hot stars and almost with the same Very hot stars and almost with the same temperature:temperature:

not explained by neutron star thermal evolution.not explained by neutron star thermal evolution.

II – Recent Observations: SGR 0418+5729, Massive and Highly Magnetized White Dwarf

Pulsars.

• SGR 0418+5729 with Period P = 9.04 s with a low surface SGR 0418+5729 with Period P = 9.04 s with a low surface magnetic field B < 7.5 x 10magnetic field B < 7.5 x 1012 12 G.G.

• Large spin down: an upper limit dP/dt < 6.0 x10Large spin down: an upper limit dP/dt < 6.0 x10-15-15s/ss/s

• Old star among SGRs: characteristic age t~ 24 MyrOld star among SGRs: characteristic age t~ 24 Myr

• Luminosity LLuminosity Lxx = 6.2 x 10 = 6.2 x 1031 31 erg/serg/s

• LLxx~ 200 dE~ 200 dErotrot/dt/dt

• To explain the luminosity an interior toroidal magnetic field 100 To explain the luminosity an interior toroidal magnetic field 100 times larger than the surface magnetic field is needed.times larger than the surface magnetic field is needed.

• High Temperature T = 0.67 KeV similar to T of new SGRs. High Temperature T = 0.67 KeV similar to T of new SGRs. N. Era, P. Esposito, R. Turolla, et al. Science, 330, 994 (2010)N. Era, P. Esposito, R. Turolla, et al. Science, 330, 994 (2010)

Massive and Highly Magnetized White Dwarf Pulsars.

• Catalogue of more than 100 isolated massive white Catalogue of more than 100 isolated massive white dwarfs and 25% are magnetic (M. Nalezyty and J. Madej dwarfs and 25% are magnetic (M. Nalezyty and J. Madej 2004) 2004)

• four most massive white dwarfs M > 1.3 Mfour most massive white dwarfs M > 1.3 Msunsun are magnetic are magnetic with B ~ 10with B ~ 106 6 -10-109 9 GG

• Magnetic white dwarfs have higher temperatures T~10Magnetic white dwarfs have higher temperatures T~1055 K K • AE Aquarii AE Aquarii : Hard X-Ray White Dwarf Pulsar found by : Hard X-Ray White Dwarf Pulsar found by

Suzaku (Y. Terada et al. 2008). Very fast and high B.Suzaku (Y. Terada et al. 2008). Very fast and high B.• Similar properties of SGR 0418+5729: P = 33 s, Similar properties of SGR 0418+5729: P = 33 s, dP/dt = 5.64 10dP/dt = 5.64 10-14 -14 s/s, Ls/s, Lxx~10~103131 erg/s (< 4 Kev), erg/s (< 4 Kev),

B = 3 x10B = 3 x1088 G , T~ 0.5 KeV G , T~ 0.5 KeV

characteristic age t~ 9.4 Myrcharacteristic age t~ 9.4 Myr

Massive and Highly Magnetized White Dwarf Pulsars.

More recently, X-ray multimirror mission (XMM) – Newton

satellite had observed a WD pulsar faster (P=13.2 s) than AE Aquarii. Mereghetti et al. 2009 showed that the X-ray pulsator RX J0648.0-4418 is a WD with mass M=1.28Msun and radius R=3000 Km.

As discussed by Mereghetti et al. 2009, the luminosity of Lx~1031 erg/s is produced by accretion onto the white dwarf of the helium-rich matter from the wind of the companion.

In this work, we investigate de possibility to describe RX J0648.0-4418 as a rotation powered WD.

Massive and Highly Magnetized White Dwarf Pulsars.

EUVE J0317-855, a hydrogen-rich magnetized WD

discovered as an extreme-ultraviolet (EUV) source by the ROSAT Wide Field Camera and Extreme Ultra-violet Explorer EUVE survey, is another observed WD pulsar candidates.

Barstow et al. 1995 obtained a period of P ~ 725 s, which is also a fast and very magnetic white dwarf with a dipole magnetic field is B ~ 4.5 × 108 G, and a mass (1.31 − 1.37)Msun

EUVE J0317-855 has a white dwarf companion, but is supposed to be no interaction between them, because of their large separation ( >103 UA).

SIMILARITIES OF SGRs WITH LOW MAGNETIC FIELD AND

WHITE DWARF PULSARS

Several features of two SGRs with low magnetic field are very similar to the ones of fast and magnetic white dwarfs recently detected.

III – Magnetar x White Dwarf Physical Scales.

• Morini (1988) andMorini (1988) and Paczynski (1990) – Massive fast Paczynski (1990) – Massive fast rotating highly magnetized white dwarf for 1E 2259+586 rotating highly magnetized white dwarf for 1E 2259+586 (AXP) at SNR G109.1-1.0 (period of P = 6.98 s)(AXP) at SNR G109.1-1.0 (period of P = 6.98 s)

• Kepler frequency W k = (G M/R3) ½ ~ (G r ) ½ ; W < Wk P ~ 1 s , the average density r > 108 g/cm3 .• Low density stars cannot spin fast .

• High density and massive white dwarfs: M= 1.4 Msun and maximal radius R ~ 1000Km = 102 RNS.

• Momentum of Inertia INS ~ M R2 = 1045 g.cm2

• IWD = 104 INS = 1049 g.cm2

Observed Long Periods as a manifestation of the low white dwarfObserved Long Periods as a manifestation of the low white dwarfmass densitiesmass densities – cannot spin faster than two seconds (Boshkayev, – cannot spin faster than two seconds (Boshkayev, Rueda, and Ruffini)Rueda, and Ruffini)

First red point – AXP unconfirmed - CXOU J171405.7-381031, P= 3.825 s

New scale of rotational energy losses

New scale of dipolar magnetic field

White Dwarf Magnetar

Soft Gamma Repeaters

Anomalus X-Ray Pulsars

Very Different Magnetic Field ScalesVery Different Magnetic Field ScalesWhite Dwarfs Magnetars

White Dwarf Model – no more ultra-strong magnetic fields, all undercritical !!!

IV – SGRs and AXPs as fast rotating-powered magnetic white dwarf Pulsars.

White Dwarf Pulsar - dErot/dt ~10^2 to 10^5 Lx

•Blue squares: SGR 1627-41 (P=2.6 s), 1E 1547.0-4950 (P=4.33s)•PSR 1627-41 (P=2.07 s) (the faster SGRs and AXPs)

White Dwarfs Neutron Star

Prediction of spin-downPrediction of spin-down lower limit of SGR 0418+5729 lower limit of SGR 0418+5729

•Maximal value of the Efficiency is one: Lx= dErot/dt

Lx P3 /(4 I) < dP/dt < 6.0 x 10-15 s/s

dP/dt > 1.18 x 10-16 s/s

dP/dt = 4.0 x 10-15 s/s (today)

V – Outbursts mechanism: change of rotational energy from glitches (spin-up events).

Delta E_rot = -2*pi^2*I*(Delta P/P)/P^2

Observed and Predicted GlitchesObserved and Predicted Glitches

VI - DIPOLE MAGNETIC MOMENT OFNEUTRON STARS AND WHITE DWARFS

Green cross points - X-ray pulsars. The two blue circle points - SGR 0418+5729 and Swift J1822.3-1606 considering neutron stars and white dwarfs parameters. The black full point are: RX J0648.0-4418, AE Aquarii and EUVE J0317-855. And all the other points points are polar and isolated white dwarfs (see Terada et al. 2008d, for details of these points).

Because of the small radius of the fast and massive white dwarf comparing to normal WD, the large magnetic field of the SGRs/AXPs as white dwarfs generated a magnetic dipole moment m (1034 - 1036) emu, exactly in the range of m for isolated and polar magnetic white dwarfs.

The values for m ~ (1033 - 1034) emu of the two SGRs with low B, are exactly at the same order of the three white dwarf pulsars observed, and in the lower values of the observed isolated and polar white dwarf magnetic dipole moment range.

Magnetic dipole moment m ~ (1034 - 1036) emu

The large steady X-ray emission Lx~1035 erg/s observed in the SGRs/AXPs is now well understood as a consequence of the fast white dwarf rotation (P ~ 10 s), since the magnetic dipole moment m is at the same scale as the one observed for the very magnetic and not so fast WDs.

This supports the description of SGRs/AXPs as belonging to a class of very fast and magnetic massive WDs perfect in line with recent astronomical observations of fast white dwarf pulsars.

CONCLUSIONS

In this new description several observational properties are easy understood and well explained as a consequence of the large radius of a massive white dwarf that manifests a new scale of mass density, moment of inertia and rotational energy:

I - The existence of stable WDs can explain, the range of long rotation periods (2 P 12 s) observed in SGRs and AXPs.

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II - The long standing puzzle of the energetic balance of the SGRs/AXPs pulsars is solved: the steady X-ray luminosity Lx observed is smaller than the loss of ̇rotational energy of the WD.

III - The large steady luminosity Lx seen of Lx ~ 1035 erg/s, for so slow pulsars (Ω ~ 1 Hz) is also understood, as a consequence of the large radius of the dense WD that produces a large magnetic dipole moment, in the range of the magnetic white dwarfs.

IV – The large dP/dt observed (10-10 - 10-13 s/s) are also consequence of the large WD magnetic dipole moment, as well of the large radius and the momentum of inertia, and not only of the magnetic field as it is the case for NS in the magnetar model.

V - The similiarity of the observational properties between SGR 0418+5729 and the white Dwarf pulsar AE Aquarii reopens the SGRs and AXPs description as rotation-powered white dwarf pulsars.

VI - Dipolar Magnetic fields all undercritical for SGRs/AXPs as white dwarfs pulsars.

VII -A theoretical predicition for the lower limit of the first derivative of the rotational period of SGR 0418+5729 was confirmed in the white dwarf model.

VIII - The energetics of all SGRs and AXPs, including their outburst , are well explained by the change of the rotational energy of white dwarfs, associated to the observed sudden spin-up changes of the rotational frequency ( normal glitches).