millisecond pulsar and khz qpos of lmxb chengmin zhang, naoc 2011 – naoc collaborators: j. wang,...
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Millisecond Pulsar and kHz QPOs of LMXB
Chengmin ZHANG, NAOC
2011 – NAOCCollaborators:
J. Wang, L.M. Song, Y.J. Lei, F. Zhang
1st PSR Discovery -- 1967; J Bell 1st MSP Discovery – 1982; D Backer (died 2010)
1967, 1st PSR, spin P= 1.33 s
1982, 1st MSP, spin P=1.56 ms
SUPERNOVA EXPLOSION
SUPERNOVA EXPLOSION – Crab Pulsar P=33 ms
Chinese Astronomer recorded Crab Nebula in 1054 AD, Song Dynasty.
It is a great glory of Chinese Ancient
Pulsar - Rotating Neutron/Quark Star
Pulsar Beacon
Pulsar: Magnetic field--period
ATNF PSR data Catlog : PSR/MSP
PSR: 2000+
MSP: ~ 200; BPSR: ~140
(2) 716 Hz; ~10^8 G; why not 10^7 G ?
(1) Two types : Normal PSR - Recycled MSP
LMXB
Crab Pulsar
毫秒脉冲星 MSP
Pulsar status (see Manchester Talk)
Pulsar : ~2000 (radio) + ~ 200 (X-ray) PSR in Binary : ~160, NS/WD/Planet MSP: ~200 , P<30ms , half/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 (670 Hz); Fastest MSP in 2006 (716 Hz)
RXTE: 24 spins, Max=619 Hz, X-ray band
Two kindsTwo kinds : : Normal and Millisecond Normal and Millisecond Pulsar ?Pulsar ?
Bimodal distribution: Magnetic B and Spin-P On ATNF PSR data, see Hobbs & Manchester 2005
Differences between PSR & MSP
Spin up : P=1.4 ms – 30 ms ; Field low : B= 10**8 G Stable : Pdot=10** ( -20 ) s/sMass: >1.4 M ? ⊙Binary: MSP (Li XD talk)
Two kinds of PSRs
• MSPs old ? P/Pdot~109 yrs
• Half binary ; B-P low 低• ‘recycled’ by accretion from binary
• accretion spins up NS to MSP
• Evidence of MSP in binary ?
Normal Pulsars: SN
• associated with supernova
• Spin Periods 0.033 – 8.5 s
• Young ? T=P/Pdot < 107 yrs
• Mostly non-binary
Millisecond Pulsars (MSPs): 1982,
Recycled, Srinivasan & Radhakrishnan (died 2011)
蟹状星云
双星系中子星 X 射线源
Accreting X-ray MSP- SAX J1808.4-3658 (2.49 ms)
Wijnands and van der Klis, 1998
MSP & Binary - 1st Evidence
Double Pulsars PSRJ0737-3039A Parkes + GBT radio telescope
P=22.7 ms , B~109 Gauss, 1.34 M⊙ , ; MSP - Recycled
P=2.8 s , B~1012 Gauss, 1.25 M ⊙ PSR - Normal
DNS (double pulsar) : M=1.25 M⊙, M=1.34 M (Lyne et al. 2004)⊙ PSR 1913+16 : M=1.38 M , M=1.4 ⊙ M (see Manchester & Taylor book)⊙
MSP & Binary - 2nd Evidence
中子星 Neutron Star
MSP is recycled in Accreting Binary,
Proposed by Srinivasan & Radhakrishnan 1982
Radhakrishnan died 2011
Theoretical model: Magnetic neutron star in Binary system
For a strong NS magnetic field, disk is disrupted in inner parts,
where most radiation is produced.
NS spinning => X-ray pulsar
Material is channeled along field lines and falls onto star at magnetic poles
Millisecond Pulsar (MSP) formation
• Accreted matters spin-up neutron star (Wang & Zhang 2011)
• Buried NS magnetic field ( van den Heuvel 2004; Zhang & Kojima 2006)
MSP spun-up by accretion: e.g. Alpar et al 1982
Millisecond Pulsar Heavier !
Mean value <M> = 1,57 +/-0.2 M⊙
Zhang & Kojima 2006, ~1012 G Strong magnetic field channels gas to magnetic poles
X-rays
Drag field lines to equator region
Magnetic Field of MSP
~108 G Magnetic field makes gas allover star surface
No drag field lines
Spherical Accretion-Bottom magnetic field 10**8 G
Strong Magnetic field equator region: ~1014 G
MSP – Bottom magnetic field 10^7.5 G ?
Initial field: 1012 G and 1013 G , Field decays with accreting mass, reaches the bottom value after accreting ~0.2 M⊙
Bottom magnetic field is defined ;
Alfven radius equals Star radius,
B proportional to accretion rate
Magnetic field vs. Spin Period relation
Evolution track in B-P diagram ; Initially, spin-up and field little decays ; Later, almost follow the spin-up line
MSP spun-up in binary accretion Wang & Zhang 2011
Magnetar ( 磁星 ) Bottom field: 10^7.5 G
If magnetar accretes 0.2 solar mass,
the bottom field of 10^7.5 Gauss !
Bottom field is independent of initials Wang, Zhang,.. et al. 2011
(Lattimer & Prakash 2006)
MSP mass : average ~1.6 M⊙ > 1.4 M⊙
63 average mass M=1.46+/-0.30 M⊙
( Zhang & Wang et al 2011 )
Statistics of 63 NS mass - Zhang et al 2011
Histogram: Gaussian Distribution
MSP Mass vs. spin period; Ps ~ 20 ms
MSP <mass> = 1.57+/-0.35 M⊙ Slow NS <mass> = 1.37+/- 0.23 M⊙ ~0.2 M ⊙ accreted in Binary - MSP added mass – spin relation: 0.43/(P/ms)^0.7 (M⊙)
How about MSP mass < 1.4 M⊙1) initial mass is low, e.g. 1.2 M ; ⊙ binding energy
2) AIC: Accretion Induced Collapse of White Dwarf find: < 20% BMPSs are involved AIC processes Dayal & Lilia (ANU) 2007
( 24/35 )
Typically: Twin KHz QPO
Upper ν2 ~ 1000 (Hz)
Lower ν1 ~ 700 (Hz)
Twin QPO difference 300 Hz
Power Density Spectra (PDS)
MSP : in Accreting BinaryX-ray Neutron Star kHz QPOs
NS/LMXBs kHz QPOs in Atoll and Z Sources
Accretion rate direction
~Eddington Accretion~1% Eddington Accretion
Hasinger & Van der Klis 1989; Hasinger 1990
Z sourceAtoll source
• Low frequency QPOs (<100Hz)
• hecto-hertz QPOs (100-200Hz)
• kHz QPOs (~200-1200+Hz): Lower and upper - twin peak QPOs
frequency
pow
er
Sco X-1
kHz QPO origin remains questionable, often expected associated to the orbital motion in the inner part of disc.
QPO bands
RXTE: Spin and kHz QPO 1996—2011
kHz QPOs (35) 127 - 1200+ Hz, van der Klis 2008; max = 1329 Hz (4U 0614)?: max = 1224 Hz ?,
Boutelier et al. (2010: 1860 Hz harmonic) Max kHz QPO > ISCO, NS surface > M – R
Spin frequency ~ Burst oscillation (26); 95 - 619 Hz, Wijnands 2008 (45 Hz >552 Hz Galloway et al 2010) Max spin 619 Hz, MSP 716 Hz (Hessels et al. 2006). Max spin > GW:
HBO Horizontal Branch Oscillation, ~ 15-70 Hz, EXOSAT 1985; RXTE 1996
NBO , ~ 5 Hz, see Yu & van der Klis 2001
BH QPO, ~ 40 - 450 Hz, McClintock & Remillard 2006
Twin kHz QPO relation
Non-linear relation:
ν1 = ~700. (Hz)(ν2 /1000Hz)b
b ~ 1.6 Atoll Source, e.g. 4U1728
b ~ 1.8 Z Source, e.g. Sco X-1
Cir X-1
dif
fere
nce
Rat
io
1. separation is constant ? (beat)
2. Ratio is a constant : 3:2 ?
BEAT ?
Ratio const ?
Twin kHz QPO distribution
Twin kHz QPO distribution; ratio~1.5=3:2 Ave.
Spin Frequency – X-ray MSP by RXTE
26 Spin sources
12 spin + kHz QPO sources
Spin frequency:
Max: 619 Hz
Min: 95 Hz
spin
Cir X-1
fittings
kHz QPO models :
1. relativistic precession
2. Alfven wave
Theoretical Explanation for kHz QPOs
Beat-frequency Model ?
Relativity precession Model
Alfven Wave Oscillation Model
Summary: new Knowledge added
MSP in 30 years: Magnetism, Spin, Mass
Bottom field B = 10^7.5 G ; Atoll - 10^8 G ; Z - 10^9 G ;
Spin P: 1.4 ms ; Max spin 700 Hz ?
Mass : <M> = 1.4+0.2 M ⊙ kHz QPOs 1300 Hz >> sub-millisecond ? 0.5 ms
Thanks To Dick Manchester for discussions
On MSP Bottom Magnetic Field Prediction,
it needs More MSPs.
Dedicated to two MSP pioneers
D. Backer & V. Radhakrishnan
Both are right ! we cannot live as long as MSP