Study on Pulsar Multi-wavelength Emission

1. Study on Pulsar Multi-wavelength Emission • Introduction • Multi-wavelength emission regions • Radio phase-resolved spectra Hong Guang Wang Center for Astrophysics, Guangzhou University

2. Multi-wavelength observational features (radio to gamma-ray) pulse profiles (light curve) ~1800 psrs (mostly radio) gamma-ray ~20 X-ray ~100 Optical (UV, IR) a few luminosity, spectrum polarization timing Radio features Single pulse (drifting, nulling, mode changing, giant pulses, microstructure)

3. P (s) rc (km) • 0.0014 66 • 0.01 480 • 4.8×104 • 8.5 4.1×105 rc=Pc/2p Light cylinder Last open field line (… closed …)

4. For pulsar magnetosphere ~ 105 km, small distance ~ 0.1kpc, the angular size is q ~ 10mas Even VLBI can not resolve. How can we know details about emission structure and physical process in pulsar magnetosphere ? Earth

5. Introduction • Multi-wavelength emission regions • Phase-resolved spectra

6. pulse profile Multiwavelength Profiles Observational features – average profiles

7. Observational features – linear polarization

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

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

10. Line of sight Density gradient Barnard & Arons 1986 Line of sight RFM or non-RFM? Low frequency High frequency Cordes 1978 Phillips 1992

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

12. Progress in methods

13. W z m a W r m LOS q r Pure geometric method(pulse width -> altitude) Assumptions: (1) static dipole (2) asymmetric emission region around W-m plane (3) last open field line Gil et al. 1984, LM 1988, Rankin 1993, Gil & Kijak 1993,1997, Wu et al. 2002 … ~200 PSRs, Emission altitude: <10% Rc

14. W m celestial sphere LOS - acceleration (E vector) Rotation vector model (RVM) • Radhakrishnan & Cook 1969, Komesaroff 1970 dipole

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

16. Time-delay method (1) timing method Cordes 1978 • Based on RFM • The total time delay: • Remove dispersion delay of ISM • Derive altitude range A dozen of pulsars: r ~ 100-500km Kramer et al. 1997

17. leading trailing Time-delay method (2) polarization method Blasckiewcz et al 1991 • 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

18. Blaskiewiscz et al. 1991, 18 PSRs @1.4GHz, average （300+/-200）km 14 PSRs @430MHz （410 +/- 260 ）km • Hoensbroech & Xilouris,1997 21 PSRs @0.430~10.45 GHz, 1%~2% Rc

19. Time-delay method(3) conal-component phase shift B0329+54 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 Before 2006, No work to constrain gamma-ray emission regions.

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 • Pulsar wind nebulae (optical, X-ray) W m colat. ext. NS azimuth ext.

22. Double-pole origin W z=113o a=74.7o m Pole 2 (IP) Pole 1 (MP) Line of Sight Radio and gamma-ray regions of B1055-52 Wang et al. 2006 MNRAS ~140o Static dipole+aberration +retardation+sweepback

23. Improved results of B1055-52 Based on improved aberration modification & new PA data (static dipole, standard RVM) Confirm: a=75deg. z=111deg. 3GHz 1.5GHz 600MHz Weltevrede1 & Wright, 2009

24. W m Plasma loaded Spitkovsky 2006 Pulsar magnetic field vacuum dipole Force-free magnetosphere static rotating Deutsch 1955, … Cheng et al. 2000… Watters et al. 2009

25. h=0.2 h=0.6 h=0.025 h=1.0 h=0.4 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 Different layers and sky map

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

27. Work Interface

28. Test Interface

29. Wang N. et al. 2004 Manchester & Johnston 1995 Radio pulsar: B1259-63 • Discovered in 1992 (Johnston et al.) • P=47.7ms, B=3.3E11 Gauss • Companion: B2e star of ~10 solar mass

30. h=0.99 h=0.9 h=0.7 h=0.5 h=0.3

31. Gamma-ray pulsars(now ~20 psrs)

32. Challenge from the Crab pulsar 前导成分 高频射电 成分 低频射电 成分

33. Constraint based on g-B absorption r>0.1rc, excluding PC model MAGIC detected 25GeV pulsation Lopez et al. 2009 Lee et al. 2009

34. B1055-52 1520MHz P=0.197s B=1.1E12 Gauss ROSAT <0.5keV` ROSAT >0.5keV OSSE 48-184keV COMPTEL 0.75-30MeV EGRET >240MeV Thompson et al. 1999

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 B1133+16 Chen J.L. et al. 2007

39. Possible interpretation?

42. Concluding remarks • Constraining 3d multi-wavelength emission region structure is important for discrimination of emission models. Multi wavelength observations need to be combined and coherently interpreted. 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. Thanks for your attention Rankin & Weisberg 2003