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Magnetic Field & Mass of Neutron Stars 中子星的磁场和质量

Magnetic Field & Mass of Neutron Stars 中子星的磁场和质量. CHENGMIN ZHANG 张承民 National Astronomical Observatories Chinese Academy of Sciences, Beijing zhangcm@bao.ac.cn. After SUPERNOVA EXPLOSION A Pulsar 。。。. SUPERNOVA EXPLOSION - Pulsar formed ?.

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Magnetic Field & Mass of Neutron Stars 中子星的磁场和质量

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  1. Magnetic Field & Mass of Neutron Stars中子星的磁场和质量 CHENGMIN ZHANG 张承民 National Astronomical Observatories Chinese Academy of Sciences, Beijing zhangcm@bao.ac.cn

  2. After SUPERNOVA EXPLOSIONA Pulsar 。。。 SUPERNOVA EXPLOSION - Pulsar formed ?

  3. PSR -- 1967; P= 1.33 s ; by J Bell MSP – 1982; P= 1.56 ms ; by D Backer (2011) Discoveries of 1st PSR and MSP

  4. OUTLINE OF TALK Pulsar (1967- 2013) magnetic field Mass Conclusions

  5. Normal Pulsar at birth spin P ~ 30msRotating Neutron Star - Quark Star Pulsar Beacon

  6. Pulsars 1967-2013 Ground-Space， ~ 2160 radio pulsars Optiacl, X-ray (Accretion NS 100 ?), Gam- ray (FERMI > 125)

  7. Part 1. Pulsar （PSR）磁场-周期

  8. Magnetic-Period diagram and 2160 PSRs (March 2013) Magnetars Pulsars Spin-up line by van den Heuvel Death line by Ruderman MSPs Bottom Field 2160PSRs (261 MSPs), data from ATNF Pulsar Catalogue in March of 2013. 212 binary pulsars including 160 MSPs.

  9. Bimodal distribution: Magnetic B and Spin-P Bimodal： Normal and Millisecond Pulsar

  10. Pulsar status (1967-2013) Pulsar： ~2160 (radio) + ~ 200 (X-ray) PSR in Binary：~ 212, NS/WD/Planet MSP: ~261， P<20ms，40% in binary Magnetic Field: 108 G - 1015 G; ~1012 G Spin period: 1.4 ms,10s, <P>=0.5s Bands: Radio, Optical, X-ray First MSP in 1982 (spin 670 Hz); Fastest MSP in 2006 (716 Hz) RXTE: 26 spins, Max=619 Hz, X-ray band; precisely measured 2 solar masses: PSR 2010

  11. Galactic Distribution of Pulsars 脉冲星空间分布 – 自行运动 proper motion of PSR & MSP 年轻的正常脉冲星银道面集中 老年的毫秒脉冲星银心区集中 Young PSR - Galactic plane old MSP - Galactic core MSP

  12. PSR-MSP（毫秒脉冲星） 两类 Normal Pulsars: SNR 超新星爆发 • Formed in supernova • Periods between 0.03 and 10 s • Relatively young (< 107 years) • Mostly single (non-binary) Crab 蟹状星云 Millisecond Pulsars: accreting spin-up in binary 双星系中吸积加速 • MSPs are very old (~109 years). • Mostly binary； B-P low 低 • ‘recycled’ by accretion from binary • accretion spins up NS to milliseconds • During the accretion X-ray binary MSP in binary 双星系中子星X 射线源

  13. Formation of MSP: recycled in Accreting Binary, Proposed by Alpar et al. 1982; Srinivasan & Radhakrishnan 1982 Proved in this decade: AMXP, DNS, etc. 中子星 Neutron Star Radhakrishnan died 2011 Magnetic, Spin, mass increases > 1.4 M⊙

  14. MSP formation: X-Ray Binary

  15. NS Magnetic field ~ 1012 G Magnetic field of SUN ~ 100 Gauss 》》 NS ~ 1012 G Magnetic flux conserved Pulsar Features：Magnetic

  16. Magnetic Strength of Astronomical Objects NS Magnetic B ~ 108G - 1015G Sun B ~ 100-1000 G Earth B~ 1 G 100,000 G - man made

  17. Crab-like Pulsars 15 Binary X-ray Pulsars 10 Magnetars/AXPs? 14 10 Radio Pulsars 13 10 12 10 11 10 10 10 9 10 NS Populations Surface Magnetic Field (G) 2160 PSRs+200 X-ray NS ms Pulsars Rotation Period (sec) 0.001 0.01 0.1 1 10 100 1000

  18. Rotation-powered: single, Radio + X-ray Accretion-powered: binary, X-ray Nuclear-powered: LMXB, X-ray burst frequency X-ray Pulsars

  19. Pulsars： magnetic dipole radiation Magnetic field estimation DNS binaries live here

  20. Origination of neutron star magnetic field Dynamo MHD: thermomagnetic effect, Blandford et al 1983, generated by convective motions in the core of the star, in same way as the Earth's magnetic field. (2) Collapsed from main sequence star, 'fossil field hypothesis' , (J. Braithwaite and H.C. Spruit: 2004, Nature, 431, 819-821 ) Solar Radius: 697,000 km, B=10^3 Gauss, collapsed to NS radius 10 km with magnetic flux conservation, 10^12 Gauss field can be obtained. (3) Permanent magnet: neutron intrinsic spin magnetic moment aligned. Core: 10^16 Gauss Surface: 10^12 Gauss

  21. Where is the Magnetic field ? Neutron Star Parameters: Mass:= 1.25 M⊙; 30 measured, (PSR 1913+16: 1.41&1.38). Radius: 15 km, inferred. Surface temperature 10^6k Magnetic field = 10^8-15 G Period=1.5ms – 10 s Position of magnetic field: Outer crust : decay fast Whole crust: : Sang & Chanmugam 87 Core: no decay

  22. Estimates of NS Magnetic Fields (1) A simple estimate, flux conservation from the progenitor star,R〜1011cm, B〜102 G →R〜106cm, B〜1012 G (2) Assume –d(Iω2/2)/dt = mag. dipole radiation; →B∝ sqrt(P*Pdot) 〜 1011~13 G (dependence of I,M,R) (3) Detection of X-ray spectral features due to (electron) cyclotron resonance ; Ea = heB/2πme =11.6 (B/1012 G) keV (4) LMXB, magnetosphere radius，~108 (G), SAXJ 1808.4-3658

  23. Observatoins with BeppoSAX Fundamental and 2nd harmonic in 4U 1909+07 Cusmano et al. Astron. Astrophys 338, 79 (1998) 4 harmonics in 4U 0115+63 Santangelo et al. Astrophys. J. 523, L85 (1998) 10 20 30 50 100 1 2 5 10 20 50 Energy (keV)

  24. Observations with RXTE Makishima et al 1992, describe cyclotron scattering resonance features 14 cyclotron line pulsars 6 discovered by RXTE/BEPSAX, Swank et al 2004(proposal) 36 kev, B=3.*1012 (G) in MX0656-072 Heindl et al 2004 41 kev, B=3.6*1012 (G) in Her X-1 Gruber et al, APJ, 562, 449 (2001)

  25. Evolution of NS Magnetic Field, A scenario before the 1990s • All NSs are born with magnetic fields (1012 G). • The magnetic field is sustained by permanent ring current, flowing possibly in the crust. • The magnetic field decays exponentially with time, due to Ohmic loss of the ring current. • Radio pulsar statistics suggest a field decay timescale of τ〜107 yr. • The older NSs (e.g., millisecond pulsars) have the weaker magnetic field.

  26. Evolution ?, Age of Pulsars Characteristic age: T=P/Pdot, Pdot=dP/dt Not a good indicator for PSR age, initial period ? Crab PSR, from 1054, ok./ MSP ? T~ Hubble age? T>t=real age ? Dipole radiation torque ? T~Z/v, Z vertical position in Galaxy, v=proper velocity. But initial Z=0? SNR age. Discrepancy ? Dipole spin down age ? PSRB1757-24/SNR G5.4-1.2, SNR age=40kyrs, T=16kyrs

  27. Magnetic field decay main mechanisms: Ohmic dissipation effect: Geppert & Urpin 1995; Chanugam 1992; many others, etc. Hall drift effect: Kojima 1994; Naito & Kojima 1994; Geppert et al 2003; Rheihardt & Geppert 2002; Jones 2003; Cumming et al 2004: Hall cascade; etc.

  28. Since middle of 1980’s B decay, automatic ? P/Pdot=age ? 1986, Kulkarni, PSR+WD, 200Myrs 1986, Taam & van den Heuvel 1989, Shibazaki, Murakami, Shaham, Nomoto, Nature PSR WD B=Bo/(1+ ∆M/mB)

  29. Magnetic evolution observations B=Bo/(1+ ∆M/mB) Taam & Heuvel 1986 Shibazaki, Murakami, Shaham & Nomoto 1989 HMXBs, binary pulsars, LMXBs

  30. Magnetic evolution observations Observations: Becker et al 2003: 3.05-ms pulsar B1821—24 in Globular Cluster M28 by Chandra, 3.3 kev line,implying B=3*10^11 Gauss. Heuvel & Bitzaraki 1995 Bottom magnetic field

  31. Accretion induced magnetic field decay Zhang et al, 1994, Ferromagnetic screening Urpin, Geppert, 1994, Ohmic dissipation Cheng, Zhang, 1998, accretion flow, Bottom B Cheng, Zhang, 2000, Bottom period Bhattacharya, 2000; spin up effects. Melatos & Phinney, Payne, Konar, Urpin, Geppert, ….2000’s

  32. Double Pulsars in Binary System

  33. PSRJ0737-3039A , J0737-3039B two pulsars lie (500-600 pc) away in our Galaxy 800,000 km, about twice the distance of Earth-Moon. orbit period 2.4 hours， 85 Myrs combining。 PSR J0737-3039 10-times closer to Earth than is PSR 1913+16 P=22。7 ms， B=10**9 Gauss, 1.34 solar mass P=2。77 s，B=10**12 Gauss, 1.25 solar mass

  34. Formation of millisecond pulsar (MSP) Millisecond X-ray pulsar by RXTE: SAXJ 1808.4-3658, P=2.49 (ms), Wijnands & van der Klis 1998 MSP is recycled by accretion: Alpar et al 1982 • Accreted matters spin-up X-ray neutron star (NS) • Buried NS magnetic field

  35. Sample: magnetic field decay in the binary phase, Double Pulsars PSRJ0737-3039A Parkes： Lyne et al Sci, 2004; Burgay et al. 2003, Nat; van den Heuvel, Sci 2004 Firstly formed PSR, P=22.7 ms， B~109 Gauss, 1.34 M⊙ P=2.8 s，B~1012 Gauss, 1.25 M⊙

  36. RXTE: Spin Frequency of X-ray PSR Spin sources: 8+12+4=24 Frequency: 190 - 619 Hz Radio MSP： 716 Hz（GBT）

  37. Accretion induced NS magnetic field decay in binary phase: theories Wijers, Hartman & Verbundt 1992 Zhang et al. 1994, screening Urpin & Geppert, 1998, Ohmic Wijers 1998, accretion rate ?, Bhattacharya & Konar 2002, Payne & Melatos 2004; Lovelace et al 2005, Zhang & Kojima 2006, Alfven R=R*

  38. Magnetic neutron stars For neutron star with a strong magnetic field, disk is disrupted in inner parts. This is where most radiation is produced. Compact object spinning => X-ray pulsator Material is channeled along field lines and falls onto star at magnetic poles

  39. X-Ray Blusters

  40. 磁场演化演示 Zhang & Kojim 2006, ~1012 GStrong magnetic field channels gas to magnetic poles X-rays Drag field lines to equator region

  41. Quasi Spherical Accretion Bottom magnetic field formed ~108 G Magnetic field makes gas allover star surface No drag field lines Strong Magnetic field equator region: ~1014 G

  42. Final Magnetic field structure of recycled neutron star Large scale field: weak 108 Gauss Local field: strong 1014-15 Gauss

  43. MSP: Bottom magnetic field Bottom magnetic field is defined by the condition; Alfven radius equalsStar radius, B is proportionally related to the accretion rate Initial field: 1012 G and 1013 G， Field decays with the accreting the mass， reaches the bottom value after accreting ~0.2 M⊙

  44. Magnetic field vs. Period relation Evolution track in B-P diagram ； Initially, spin-up and field little decays； Later, almost follow the spin-up line

  45. Main Conclusion on Pulsar：Future detection • ~107 (G) MSP, exists ? Magnetar accreted 0.2 solar mass >> MSP !

  46. Maximum Magnetic Field of NS Crust modulus, 10^13 G Cyclotron line, 10^13 G AXP, SGR, 10^14-15 G ? Mc^2, 10^18 G Gravity energy, 10^17 G Gravitational wave limit, 10^16 G GW braking index n=4, Obs n<3.

  47. Magnetic Field and EOS Magnetic pressure B^2 ~ 10^29 B15^2 Crust structure of NS/QS ? Quark or electron degenerate ?

  48. Magnetar 10^15 G Soft Gamma Repeater (SGR)

  49. Magnetar: a super-strong magnetic field ? Theory by Dr.Robert Duncan (1992) Observation: Crysa Kouveliotou (2003) SGR 1806-20 T=7.5 s magnetic field 10^15 G Normal radio pulsars reach 10^12 G

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