1 study on pulsar multi-wavelength emission hong guang wang center for astrophysics, guangzhou...
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Study on Pulsar Study on Pulsar Multi-wavelength Emission Multi-wavelength Emission
Hong Guang WangHong Guang WangCenter for Astrophysics, Guangzhou UniversityCenter for Astrophysics, Guangzhou University
IntroductionIntroduction Multi-wavelength emission regionsMulti-wavelength emission regions Radio phase-resolved spectraRadio phase-resolved spectra
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Multi-wavelength observational features(radio to gamma-ray)
pulse profiles (light curve)
luminosity, spectrum
polarization
timing
Radio features
Single pulse (drifting, nulling, mode changing, giant pulses, microstructure)
~1800 psrs (mostly radio)
gamma-ray ~20 X-ray ~100 Optical (UV, IR) a few
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rc=Pc/2Light cylinderP (s) rc (km)0.0014 660.01 480 1
×104
8.5 4.1×105
Last open field line(… closed …)
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For pulsar magnetosphere ~ 105 km, small distance ~ 0.1kpc, the angular size is
Earth
Even VLBI can not resolve.
~ 10as
How can we know details about emission structure and physical process in pulsar magnetosphere ?
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IntroductionIntroduction Multi-wavelength emission regionsMulti-wavelength emission regions Phase-resolved spectraPhase-resolved spectra
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Observational features – average profiles
pulse profile
Multiwavelength Profiles
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Observational features – linear polarization
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Related issuesRelated issues
Origin of gamma-ray emissionOrigin of gamma-ray emission
(polar cap, outer gap, slot gap, annular (polar cap, outer gap, slot gap, annular gap?)gap?)
Radius-to-frequency mapping (RFM)Radius-to-frequency mapping (RFM) Beam structureBeam structure
……
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Coroniti 1990
Origin of multi-wavelength emissionOrigin of multi-wavelength emission
BLight
Cylinder
closed fieldregion
polarcap
null charge surface. B = 0
slot gap
Inner gap
Dipole fieldDipole field
Induced electric field, Induced electric field, acceleration gapacceleration gap
Relativistic particlesRelativistic particles => multi-wavelength emi=> multi-wavelength emissionssion
Uncertainty in emission regionRadio: whole open field lines?High energy: which kind of gap?
Annular gap
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RFM or non-RFM?RFM or non-RFM?
Low frequency
High frequency
Line of sight
Phillips 1992
Cordes 1978
Line of sight
Density gradient
Barnard & Arons 1986
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Beam structure ?Beam structure ?
Rankin 1983
outer coneinner cone
coreOuter cone
inner conecore
Inverse Compton scattering model Lin & Qiao 1998
Curvature models(e.g. Gil et al.)
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Progress in methodsProgress in methods
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Pure geometric methodPure geometric method(pulse width -> altitude)(pulse width -> altitude)
Assumptions:Assumptions:
(1) static dipole(1) static dipole
(2) asymmetric emission region around (2) asymmetric emission region around -- plane plane
(3) last open field line(3) last open field line W
r
LOS
~200 PSRs, Emission altitude: <10% RcGil et al. 1984, LM 1988, Rankin 1993, Gil & Kijak 1993,1997, Wu et al. 2002 …
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celestial sphere
LOS
Rotation vector model (RVM)Rotation vector model (RVM) Radhakrishnan & Cook 1969, Komesaroff 1970Radhakrishnan & Cook 1969, Komesaroff 1970
-
acceleration(E vector)
dipole
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Problems of pure geometric methodProblems of pure geometric method aberration effectaberration effect
retardation effect retardation effect
sweep-back effect sweep-back effect
aberration effect retardation effect
Rotation direction
r<<Rc
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Time-delay method (1) timing methodTime-delay method (1) timing method Based on RFMBased on RFM The total time delay:The total time delay:
Remove dispersion delay of Remove dispersion delay of ISMISM
Derive altitude rangeDerive altitude range
Kramer et al. 1997
A dozen of pulsars:A dozen of pulsars: r ~ 100-500kmr ~ 100-500km
Cordes 1978
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Time-delay method (2) polarization methodTime-delay method (2) polarization method
aberration & retardation aberration & retardation effects modifiedeffects modified
Time delay of the “center” Time delay of the “center” of position angle curve to of position angle curve to that of pulse profilethat of pulse profile
Applicable to pulsars with Applicable to pulsars with “S”-shaped PA curves“S”-shaped PA curves
Blasckiewcz et al 1991
leading trailing
Blasckiewcz et al 1991
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Blaskiewiscz et al. 1991, Blaskiewiscz et al. 1991,
18 PSRs @1.4GHz, average 18 PSRs @1.4GHz, average (( 300+/-200300+/-200)) kmkm
14 PSRs @430MHz 14 PSRs @430MHz (( 410 +/- 260 410 +/- 260 )) km km
Hoensbroech & Xilouris,1997Hoensbroech & Xilouris,1997
21 PSRs @0.430~10.45 GHz, 1%~2% Rc21 PSRs @0.430~10.45 GHz, 1%~2% Rc
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Time-delay methodTime-delay method (3) conal-component phase shift(3) conal-component phase shift B0329+54
Gupta and Gangadhara (2001,2003)Gupta and Gangadhara (2001,2003)
7 PSRs at 325MHz, 600MHz, 7 PSRs at 325MHz, 600MHz, 200-2,000 km (0.5%~4% Rc).200-2,000 km (0.5%~4% Rc).
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Methods to constrain radio emission regions
No work to constrain gamma-ray emission regions.Before 2006,
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3d ? Multi-wavelength ?3d ? Multi-wavelength ?Constrain emission regions Constrain emission regions
with:with:
Pulse widthPulse width Position angle sweep Position angle sweep Gamma-ray pulsars: Gamma-ray pulsars: light curve width & phase light curve width & phase
offset with respect to radio offset with respect to radio profilesprofiles
Pulsar wind nebulae Pulsar wind nebulae (optical, X-ray)(optical, X-ray)
NS
colat. ext.
azimuth ext.
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Wang et al. 2006 MNRAS
Line of Sight
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Pole 1
(MP)
Pole 2(IP)
Double-pole origin
Static dipole+aberration+retardation+sweepback
Radio and gamma-ray regions of B1055-52
~140o
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Weltevrede1 & Wright, 2009
Confirm: =75deg. =111deg.
Based on improved aberration modification & new PA data(static dipole, standard RVM)
Improved results of B1055-52
3GHz1.5GHz600MHz
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Pulsar magnetic fieldPulsar magnetic field
static rotating
Deutsch 1955, … Cheng et al. 2000…Watters et al. 2009
Plasma loaded Spitkovsky 2006
vacuum dipole Force-free magnetosphere
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=1.0=0.6=0.4=0.2=0.025
Different layers and sky map
A numerical 3d method to constrain emission regionsA numerical 3d method to constrain emission regions (Wang et al. 2006)(Wang et al. 2006)(1) rotating vacuum dipole (multi layers)(1) rotating vacuum dipole (multi layers)
(2) aberration + retardation(2) aberration + retardation
(3) polarization direction along curvature radius, aberration modified(3) polarization direction along curvature radius, aberration modified
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model PA curve model PA curve
Black: =1.0Red: =0.8Green: =0.6
r< 2Rc
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Work Interface
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Test Interface
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Radio pulsar: B1259-63Radio pulsar: B1259-63• Discovered in 1992 (Johnston et al.)• P=47.7ms, B=3.3E11 Gauss•Companion: B2e star of ~10 solar mass
Wang N. et al. 2004
Manchester & Johnston 1995
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=0.99
=0.9=0.7
=0.5
=0.3
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Gamma-ray pulsarsGamma-ray pulsars
(now ~20 psrs)(now ~20 psrs)
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前导成分
低频射电
成分
高频射电
成分
Challenge from the Crab pulsar
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MAGIC detected 25GeV pulsation
Lopez et al. 2009
Constraint based on -B absorption
Lee et al. 2009
r>0.1rc, excluding PC model
34 Thompson et al. 1999
1520MHz
ROSAT <0.5keV`
ROSAT >0.5keV
OSSE 48-184keV
COMPTEL 0.75-30MeV
EGRET >240MeV
B1055-52B1055-52
P=0.197sB=1.1E12 Gauss
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Vela & Vela-likeVela & Vela-like EGRET SourcesEGRET Sources
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Vela-like: (Fermi discoveries)Vela-like: (Fermi discoveries)
Abdo et al. 2009a,b,c,d, ApJ
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IntroductionIntroduction Multi-wavelength emission regionsMulti-wavelength emission regions Radio Phase-resolved spectraRadio Phase-resolved spectra
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Radio phase-resolved spectra of B1133+16
Chen J.L. et al. 2007
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Possible interpretation?
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Concluding remarksConcluding remarks
(1)(1) Constraining 3d multi-wavelength emission region Constraining 3d multi-wavelength emission region structure is important for discrimination of emission structure is important for discrimination of emission models. models.
Multi wavelength observations need to be Multi wavelength observations need to be combined and coherently interpreted. combined and coherently interpreted.
Weak model-dependent methods are needed to Weak model-dependent methods are needed to constrain the geometry.constrain the geometry.
(2) Radio phase resolved spectra + emission geometry (2) Radio phase resolved spectra + emission geometry provide a window to study the anisotropy in physical provide a window to study the anisotropy in physical conditions or process in pulsar magnetosphere. conditions or process in pulsar magnetosphere.
43 Rankin & Weisberg 2003
Thanks for your attentionThanks for your attention