1. 03/19/2007N. Bucciantini: Hubble Symposium 2007 1 Relativistic Outflows from Compact Rotators: Pulsar Winds, Pulsar-Wind Nebulae, and GRBs environment Niccolo’ Bucciantini Astronomy Department UC Berkeley http://www.astro.berkeley.edu In collaboration with: Jonathan Arons, Eliot Quataert, Todd A. Thompson, Luca Del Zanna, Elena Amato, Delia Volpi, Brian Metzger

2. 03/19/2007N. Bucciantini: Hubble Symposium 2007 2 Outline Introduction to pulsar winds Acceleration of relativistic winds Winds from proto-magnetar. Proto-magnetars as engine for GRBs. Interaction of the wind with the environment PWNe - MHD models and what we can learn from observations. GRBs as scaled version of PWNe. Reviving the magnetar scenario.

3. 03/19/2007N. Bucciantini: Hubble Symposium 2007 The NS magnetosphere Acceleration of particle pair plasma- ions from the surface: Initial Lorentz factor ~ 100 Cold wind (Sync. losses) Pair creations - change density exceeding the GJ value MHD regime (ideal?) Unipolar inductor (AGN, GRB, Magnetar) EM extraction of rotational energy.

4. 03/19/2007N. Bucciantini: Hubble Symposium 2007 At best we require a 2D axisymmeric RMHD “Steady state” No exact solution even for the simple monopole-like case Conversion of magnetic energy is logarithmic after the fast p. No collimation for a relativistic wind Terminal  =  1/3

5. 03/19/2007N. Bucciantini: Hubble Symposium 2007 MHD simulations (split monopole) Pressureless RMHD trans alfvenic solution (Bogovalov 2001) Full GRMHD simulations, subslow injection (Bucciantini et al.)  =2  =7 Magnetic surface close to monopole shape for  > 10

6. 03/19/2007N. Bucciantini: Hubble Symposium 2007 6 The force-free dipole Gruzinov 05 ff - steady state Spitkovsky 05 Closed zone extends to the LC The wind in the far region is monopolar No evidence for collimation

7. 03/19/2007N. Bucciantini: Hubble Symposium 2007 Proto-magnetars and GRBs Proto-Magnetar model - initial neutrino driven wind (Thompson et al. 2003) Rotating magnetar ( ~0.2c) Non cold atmosphere (C s ~ 0.1c, H ~ 0.1 R NS ) Surface Density ~ 10 13 g/cm 3 Surface Magnetic field B ~ 10 14-16 G PulsarsProto-Magnetars Pulsar winds are almost force freeConditions changes in few seconds from mass loaded to magnetic dominated Particles are injected with high Lorentz factorInjection is subsonic and the flow velocity at the base of the star is much smaller than c Low density in the wind might lead to charge starvation and non ideal MHD High particle density can guarantee MHD currents

8. 03/19/2007N. Bucciantini: Hubble Symposium 2007 8 Validity of the Pulsar analogy Can a magnetar trigger a GRB (efficient acceleration) Does mass flux depend on the value of B (i.e. acceleration) How energy and angular momentum losses scale with B 2 /r Can the magnetar wind inflate a bubble of magnetic field and relativistic particles inside the progenitor? Can we use what we know about pulsar winds for proto-magnetars? How good is the force-free regime How collimation and acceleration depend on What about the interaction with the environment?

9. 03/19/2007N. Bucciantini: Hubble Symposium 2007 2D Monopole Uniform radial magnetic field, density and pressure At the star boundary Vr, Bq, Bf, are extrapolated (B=2 10 15 G, r=10 10 g/cm 3, c s =0.2c) - 10 -5 M ¤ /s

10. 03/19/2007N. Bucciantini: Hubble Symposium 2007 Energy and angular momentum Angular momentum flux ~ sin 2 (  ) Energy flux ~ sin 2 (  ) Poynting flux dominated outflow E matter /E em ~ 0.1 The ratio of particle to magnetic energy ~ A + B sin (  )

11. 03/19/2007N. Bucciantini: Hubble Symposium 2007 Dipole Closed zone (R c ~ 2 R NS ) Equatorial channel (most of the mass, angular mom., and energy flux in the equator) Collimation is efficient The far zone resemble a monopole - lower equatorial velocity 

12. 03/19/2007N. Bucciantini: Hubble Symposium 2007 12 Far wind region and evolution Collimation in the far region (10 9 cm) - efficient collimation and energy conversion isotropic wind and close to equipartition energy flux close to FF, high magnetization

13. 03/19/2007N. Bucciantini: Hubble Symposium 2007 13 Magnetars as engine for GRBs Can a magnetar be the engine producing the GBR jet? NO It is not possible in Ideal MHD to achieve both, relativistic speeds and energy collimation (no evidence for sheet-like explosions). Relativistic speeds require high sigma (later evolution) Collimation requires low sigma What happen when this wind interacts with the progenitor? Can somehow collimation be achieved not because of the source but because of the interaction? What happen when this wind interacts with the progenitor? Can somehow collimation be achieved not because of the source but because of the interaction?

14. 03/19/2007N. Bucciantini: Hubble Symposium 2007 Pulsar Wind Nebulae PWNe are hot bubbles (plerions) emitting non-thermal radiation (synchrotron) at all wavelengths: require injection of relativistic particles and magnetic fields Originated by the interaction of the ultra-relativistic magnetized pulsar wind with the expanding SNR dense ejecta Crab Nebula in optical: central amorphous mass (continuum) + external filaments (lines) PWN SNR

15. 03/19/2007N. Bucciantini: Hubble Symposium 2007 Jet-torus structure: Chandra X-ray images Crab nebula ( Weisskopf et al., 2000; Hester et al., 2002 ) Vela pulsar ( Helfand et al., 2001; Pavlov et al., 2003 ) Other objects: PSR 1509-58, G0.9+01, G54.1+0.3 Crab Vela

16. 03/19/2007N. Bucciantini: Hubble Symposium 2007 TS structure and flow pattern  =0.003 The wind anisotropy shapes the TS structure. A complex flow pattern arises: A: ultrarelativistic pulsar wind B: subsonic equatorial outflow C: supersonic equatorial funnel D: super-fastmagnetosonic flow a: termination shock front b: rim shock c: fastmagnetosonic surface

17. 03/30/2007N. Bucciantini: Modeling PWNe PWN elongation Shape of the nebula - magnetic pinching ( Begelman & Li, 1992, van der Swaluw 2003, Del Zanna et al 2004 ) - average magnetization in the wind:

18. 03/30/2007N. Bucciantini: Modeling PWNe 18 Internal pressure structure Due to magnetic pinch the pressure is much higher on the axis than at the equator Hot plasma + toroidal magnetic field If the high-scale is small then the pressure acts along the axis as for a jet Begelman & Li 92

19. 03/19/2007N. Bucciantini: Modeling PWNe 19 Magnetic cavity inside progenitors What happens if a magnetar wind inflates a relativistic bubble inside a progenitor? Elongation is a strong function of magnetization

20. 03/19/2007N. Bucciantini: Hubble Symposium 2007 Dependence on the field shape Initial magnetic field with a narrow equatorial neutral sheet b=10

21. 03/19/2007N. Bucciantini: Hubble Symposium 2007 Features origin Main torus Inner ring (wisps structure) Knot Back side of the inner ring No jet - Axisymmetric assumption Knot Ring Torus Hester et al. 1995

22. 03/19/2007N. Bucciantini: Modeling PWNe Striped wind and jet properties What effect has the striped wind region size on the appearance of the jet? Where the wind magnetization is maximum? Equatorial region or polar? Wind with higher polar magnetization proposed by Arons 1998.  =0.025, b=10

23. 03/19/2007N. Bucciantini: Modeling PWNe Photon Index Brighter inner ring Mori 02 Higher index in the torus (recompression and boosting) Jet not correctly reproduced (required reacceleration)

24. 04/03/2007N. Bucciantini: Modeling PWNe Formation of polar jets by hoop stresses  =0.003  =0.03  =0.01 The global nebular flow changes with  For high magnetization (  > 0.01) a supersonic jet is formed PSR winds are below equipartition (dissipation non-ideal MHD) Proto-magnetar wind are more magnetized -> faster jet?

25. 03/19/2007N. Bucciantini: Hubble Symposium 2007 Summary and conclusions PSR magnetosphere are prototype of compact accelerators Difficulty in achieving high Lorentz factor Collimation of relativistic wind is prevented by El.field Magnetar might develop late time relativistic winds Magnetar are unlikely candidate for GRB jet Many PWNe show a jets (Crab, Vela, …) Jet collimation forbidden in the wind. Inside PWN. PWNe are elongated - axial pressure is higher despite equatorial energy flow. Magnetars inside progenitor might produce elongated cavities Elongation might be at the origin of jet-like flows - no need for collimation at the source Thank you