1. Physics and Observations of Pulsar Wind Nebulae
Stephen C.-Y. Ng
HKU

2. Why Study PWNe? Important TeV sources Cosmic ray acceleration
Relativistic shock physics
27 TeV PWNe: main Galactic TeV sources

3. Why Study PWNe? Important TeV sources Cosmic ray acceleration
Relativistic shock physics
Aguilar et al. (2013)
e+ excess: dark matter decay? Or pulsars/PWNe?
16/8/18
VHEPU

4. Why Study PWNe? Important TeV sources Cosmic ray acceleration
Relativistic shock physics
Sironi & Spitkovsky (2011)
16/8/18
VHEPU

5. Pulsars Rapidly spinning, strongly magnetized neutron stars 𝐵≈ 10 12 G
𝑃=10−100ms
𝐸∼ 𝑃 −1 𝐵 12 Vc m −1
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VHEPU

6. Pulsar Wind Where does pulsar rotational energy go? 𝐸 >1035erg s −1
< 10% in radiation (mostly -rays)
> 90% in pulsar winds
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VHEPU

7. Pulsar Wind
D. Page

8. Pulsar Wind Nebula
Cerutti et al. (2014)
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VHEPU

9. Pulsar Wind Nebula

10. Broadband Emission
NASA/CXC/ESA/2MASS/NRAO
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VHEPU

11. Crab Nebula
Synchrotron IC
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Abdo et al. (2010a)

12. Radio PWNe Synchrotron cooling time: Preserve injection spectrum
𝑡 𝑐𝑜𝑜𝑙 ≈2× 𝐵 10𝜇G − 𝜈 1GHz − 1 2 yr
Preserve injection spectrum
Trace pulsar motion to reveal birth site
Polarization observations => B-field structure
Another regime
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VHEPU

13. X-ray PWNe Synchrotron cooling time: Fast cooling time
𝑡 𝑐𝑜𝑜𝑙 ≈1.2× 𝐵 10𝜇G − 𝐸 1keV − 1 2 yr
Fast cooling time
Most recent conditions
Another regime
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VHEPU

14. TeV PWNe TeV emitting particles: X-ray emitting particles:
𝐸 𝑒 =19 𝐸 1TeV TeV
X-ray emitting particles:
𝐸 𝑒 =70 𝐵 10𝜇G − 𝐸 1keV TeV
IC cooling time:
𝑡 𝑐𝑜𝑜𝑙 ≈5.9× 𝐸 1TeV −1 𝑈 rad 0.26eVc m −3 −1 yr
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15. PWN Evolution
van der Swaluw et al. (2003)
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16. Free Expansion
van der Swaluw et al. (2003)
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17. Toroidal B-field
Porth et al. (2014)
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18. Torus+Jet Crab Vela Kes 75 G54.1+0.3 3C 58 Sewead et al. (2006)
Pavlov et al. (2001)
Vela
Kes 75
Ng et al. (2008)
Temim et al. (2010) G
Slane et al. (2004)
3C 58
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VHEPU

19. Torus Modeling Ng & Romani (2004; 2008) Crab Vela B1706-44 J2221+6114
J / G J B
J / 3C58
J / G
Viewing geometry
J / N157B B
J / G
Ng & Romani (2004; 2008)

20. Time Variability
Highly dynamic systems
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NASA/ASU/Hester

21. Vela Jet
Durant et al. (2013)
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22. Crab -ray Flares
Buehler et al. (2012)
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23. Crab Flares
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Striani et al. (2013)

24. Flare Spectrum
Weisskopf et al. (2013)
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25. PSR J18460258 / Kes 75 1 1 Integral 20-100keV Chandra 0.5-10keV
McBride et al. (2008)
Djannati-Atai et al. (2007)

26. PSR J18460258 / Kes 75
2000
2006
2009
Ng et al. (2008); Livingstone, Ng et al. (2011)
Reynolds et al. (2018)
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27. Hand of God: MSH 15–52
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NASA/CXC/SAO/Slane et al.

28. Hand of God: MSH 15–52
Abdo et al. (2010b)
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29. Hand of God: MSH 15–52 NuSTAR INTEGRAL Forot et al. (2006)
An et al. (2014)
Forot et al. (2006)
INTEGRAL
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30. Hand of God: MSH 15–52 Fermi LAT H.E.S.S. Aharonian et al. (2005)
Abdo et al. (2010b)
Fermi LAT
H.E.S.S.
Aharonian et al. (2005)
Aharonian et al. (2005)
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31. Hand of God: MSH 15–52
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Leung, Ng, et al. (in prep.)

32. Hand of God: MSH 15–52 Preliminary Preliminary
Leung, Ng, et al. (in prep.)
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VHEPU

33. Hand of God: MSH 15–52 Preliminary Preliminary
Leung, Ng, et al. (in prep.)
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VHEPU

34. Reverse-Shock Interaction
van der Swaluw et al. (2003)
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35. The Snail G327.1–1.1
Radio/ X-ray
Temim et al. (2009)
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36. The Snail G327.1–1.1 Radio TeV HESS Collaboration (2018)
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Ma, Ng, et al. (2016)

37. 16/8/18
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Temim et al. (2015)

38. Vela X Chandra H.E.S.S. Chandra INTEGRAL Fermi Mattana et al. (2011)
Durant et al. (2013)
Chandra
Vela X
Aharonian et al. (2006)
H.E.S.S.
Chandra
Mattana et al. (2011)
Mattana et al. (2011)
INTEGRAL
Grondin et al. (2013)
Fermi
radio x-ray offset
NASA/SAO/CXC
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VHEPU

39. Vela X
Slane et al. (2018)
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VHEPU

40. Bow Shock
van der Swaluw et al. (2003)
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VHEPU

41. Bow Shocks Supersonic motion in the ISM  bow shocks ISM ram pressure
Pulsar wind pressure
CXC/Weiss
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VHEPU

42. Geminga PWN Chandra HAWC Abeysekara et al. (2017)
Posselt et al. (2017)
Chandra
Abeysekara et al. (2017)
HAWC
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VHEPU

43. Elongated PWNe The Frying Pan The Snail Ma, Ng et al. (2016)
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44. PSR J1509–5850
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Romanova et al. (2005)
Ng et al. (2010)

45. PSR J1015–5719 Guitar Nebula Ng et al. (2017) Kerkwijk & Ingle (2008)
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46. Lighthouse Nebula
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VHEPU
Pavan et al (2014)

47. Lighthouse Nebula
Preliminary
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Wen, Ng, et al. (in prep.)

48. Modeling PWNe Hydrodynamic simulations MHD simulations
Temim et al. (2015)
Modeling PWNe
Hydrodynamic simulations
Reverse shock / ISM interaction
MHD simulations
Assume B-field geometry, latitude dependent wind, injection spectrum
Multiwavelength spectra
Pulsar/SNR and particle evolution
Volpi et al. (2008)
Gelfand et al. (2009)
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VHEPU

49. Open Questions Ab initio: from magnetosphere to termination shock?
𝜎-problem?
Particle acceleration in relativistic shocks?
Variability?
Jet formation?
Protons/ions in pulsar wind?
Cosmic ray diffusion in PWNe?
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VHEPU

50. Future Prospects
CTA
ATHENA / IXPE / eXTP
SKA

51. Summary PWNe are important:
TeV sources in the Galaxy
laboratories for studying relativistic shock physics
cosmic ray acceleration sites
TeV emission found at different evolutionary stages
Multiwavelength observations/modeling needed
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VHEPU