1 Study on Pulsar Multi-wavelength Emission Hong Guang Wang Center for Astrophysics, Guangzhou University  Introduction  Multi-wavelength emission regions  Radio 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 r c =Pc/2  Light cylinder P (s) r c (km)  × ×10 5 Last open field line (… closed …)

4 For pulsar magnetosphere ~ 10 5 km, small distance ~ 0.1kpc, the angular size is Earth Even VLBI can not resolve.  ~ 10  as How can we know details about emission structure and physical process in pulsar magnetosphere ?

5  Introduction  Multi-wavelength emission regions  Phase-resolved spectra

6 Observational features – average profiles pulse profile Multiwavelength Profiles

7 Observational features – linear polarization

8 Related issues  Origin of gamma-ray emission (polar cap, outer gap, slot gap, annular gap?) (polar cap, outer gap, slot gap, annular gap?)  Radius-to-frequency mapping (RFM)  Beam structure …

9 Coroniti 1990 Origin of multi-wavelength emission  B  Light Cylinder closed field region polar cap null charge surface . B = 0 slot gap Inner gap  Dipole field  Induced electric field, acceleration gap  Relativistic particles => multi-wavelength emission => multi-wavelength emission Uncertainty in emission region Radio: whole open field lines? High energy: which kind of gap? Annular gap

10 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 ? Rankin 1983 outer cone inner cone core Outer cone inner cone core  Inverse Compton scattering model Lin & Qiao 1998  Curvature models (e.g. Gil et al.)

12 Progress in methods

13 Pure geometric method (pulse width -> altitude) Assumptions: (1) static dipole (2) asymmetric emission region around  -  plane (3) last open field line W  r LOS   ~200 PSRs, Emission altitude: <10% Rc Gil et al. 1984, LM 1988, Rankin 1993, Gil & Kijak 1993,1997, Wu et al …    

14 celestial sphere   LOS Rotation vector model (RVM)  Radhakrishnan & Cook 1969, Komesaroff acceleration (E vector) dipole

15 Problems of pure geometric method  aberration effect  retardation effect  sweep-back effect aberration effectretardation effect Rotation direction r<<Rc

16 Time-delay method (1) timing method  Based on RFM  The total time delay:  Remove dispersion delay of ISM  Derive altitude range Kramer et al A dozen of pulsars: r ~ km r ~ km Cordes 1978

17 Time-delay method (2) polarization method  aberration & retardation effects modified  Time delay of the “center” of position angle curve to that of pulse profile  Applicable to pulsars with “S”-shaped PA curves Blasckiewcz et al 1991 leading trailing Blasckiewcz et al 1991

18  Blaskiewiscz et al. 1991, 18 average （ 300+/-200 ） km 18 average （ 300+/-200 ） km 14 （ 410 +/- 260 ） km 14 （ 410 +/- 260 ） km  Hoensbroech & Xilouris, GHz, 1%~2% Rc 21 GHz, 1%~2% Rc

19 Time-delay method (3) conal-component phase shift B Gupta and Gangadhara (2001,2003) 7 PSRs at 325MHz, 600MHz, 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 ? Constrain emission regions with:  Pulse width  Position angle sweep  Gamma-ray pulsars: light curve width & phase offset with respect to radio profiles light curve width & phase offset with respect to radio profiles  Pulsar wind nebulae (optical, X-ray) NS   colat. ext. azimuth ext.

22 Wang et al MNRAS   Line of Sight     Pole 1 (MP) Pole 2 (IP) Double-pole origin Static dipole+aberration +retardation+sweepback Radio and gamma-ray regions of B ~140 o

23 Weltevrede1 & Wright, 2009 Confirm:  =75deg.  =111deg. Based on improved aberration modification & new PA data (static dipole, standard RVM) Improved results of B GHz 1.5GHz 600MHz

24 Pulsar magnetic field static rotating Deutsch 1955, … Cheng et al. 2000… Watters et al 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 regions (Wang et al. 2006) (1) rotating vacuum dipole (multi layers) (2) aberration + retardation (3) polarization direction along curvature radius, aberration modified

26 model PA curve Black:  =1.0 Red:  =0.8 Green:  =0.6 r< 2Rc

27 Work Interface

28 Test Interface

29 Radio pulsar: B Discovered in 1992 (Johnston et al.) P=47.7ms, B=3.3E11 Gauss Companion: B2e star of ~10 solar mass Wang N. et al Manchester & Johnston 1995

30  =0.99  =0.9  =0.7  =0.5  =0.3

31 Gamma-ray pulsars (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 Constraint based on  -B absorption Lee et al r>0.1rc, excluding PC model

34 Thompson et al MHz ROSAT <0.5keV` ROSAT >0.5keV OSSE keV COMPTEL MeV EGRET >240MeV B P=0.197s B=1.1E12 Gauss

35 Vela & Vela-like EGRET Sources

36 Vela-like: (Fermi discoveries) Abdo et al. 2009a,b,c,d, ApJ

37  Introduction  Multi-wavelength emission regions  Radio Phase-resolved spectra

38 Radio phase-resolved spectra of B Chen J.L. et al. 2007

39 Possible interpretation?

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42 Concluding remarks (1) Constraining 3d multi-wavelength emission region structure is important for discrimination of emission models. Multi wavelength observations need to be combined and coherently interpreted. Multi wavelength observations need to be combined and coherently interpreted. Weak model-dependent methods are needed to constrain the geometry. Weak model-dependent methods are needed to constrain the geometry. (2) Radio phase resolved spectra + emission geometry provide a window to study the anisotropy in physical conditions or process in pulsar magnetosphere.

43 Rankin & Weisberg 2003 Thanks for your attention