1

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

2

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

3

rc=Pc/2Light cylinderP (s) rc (km)0.0014 660.01 480 1

×104

8.5 4.1×105

Last open field line(… closed …)

4

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 ?

5

IntroductionIntroduction Multi-wavelength emission regionsMulti-wavelength emission regions Phase-resolved spectraPhase-resolved spectra

6

Observational features – average profiles

pulse profile

Multiwavelength Profiles

7

Observational features – linear polarization

8

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

……

9

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

10

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

11

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.)

12

Progress in methodsProgress in methods

13

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 …

14

celestial sphere

LOS

Rotation vector model (RVM)Rotation vector model (RVM) Radhakrishnan & Cook 1969, Komesaroff 1970Radhakrishnan & Cook 1969, Komesaroff 1970

-

acceleration(E vector)

dipole

15

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

16

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

17

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

18

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

19

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).

20

Methods to constrain radio emission regions

No work to constrain gamma-ray emission regions.Before 2006,

21

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.

22

Wang et al. 2006 MNRAS

Line of Sight

11

Pole 1

(MP)

Pole 2(IP)

Double-pole origin

Static dipole+aberration+retardation+sweepback

Radio and gamma-ray regions of B1055-52

~140o

23

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

24

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

25

=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

26

model PA curve model PA curve

Black: =1.0Red: =0.8Green: =0.6

r< 2Rc

27

Work Interface

28

Test Interface

29

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

30

=0.99

=0.9=0.7

=0.5

=0.3

31

Gamma-ray pulsarsGamma-ray pulsars

(now ~20 psrs)(now ~20 psrs)

32

前导成分

低频射电

成分

高频射电

成分

Challenge from the Crab pulsar

33

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

35

Vela & Vela-likeVela & Vela-like EGRET SourcesEGRET Sources

36

Vela-like: (Fermi discoveries)Vela-like: (Fermi discoveries)

Abdo et al. 2009a,b,c,d, ApJ

37

IntroductionIntroduction Multi-wavelength emission regionsMulti-wavelength emission regions Radio Phase-resolved spectraRadio Phase-resolved spectra

38

Radio phase-resolved spectra of B1133+16

Chen J.L. et al. 2007

39

Possible interpretation?

40

41

42

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