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On the CR spectrum released by a type II SNR e xpanding in the presupernova wind

Astroparticle Physics 2014 23-28 June 2014, Amsterdam. On the CR spectrum released by a type II SNR e xpanding in the presupernova wind. Martina Cardillo, Pasquale Blasi , Elena Amato INAF- Osservatorio Astrofisico di Arcetri. June 23, 2014. Index.

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On the CR spectrum released by a type II SNR e xpanding in the presupernova wind

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  1. AstroparticlePhysics 2014 23-28 June 2014, Amsterdam On the CR spectrumreleased by a type II SNR expanding in the presupernovawind Martina Cardillo, Pasquale Blasi, Elena Amato INAF-OsservatorioAstrofisico di Arcetri June 23, 2014

  2. Index • Expectations from Bell non-resonant instability: • Why do we need it? • Maximum energy • Description of our toy-model: • Spectrum • Energetics • Comparison with KASKADE-GRANDE data • Comparison with ARGO data • Conclusions

  3. Non-resonant Bell Instability RESONANT INSTABILITY (Skilling 1975) Excitation of Alfvén waves with λ≅ rL Purely growing waves at wavelengths non-resonant with rL(λ<< rL), driven by the CR current jCR. NON RESONANT INSTABILITY (Bell 2004) Growth rate dependence on the shock velocity (α vs2) and on plasma density (αn⅙) Very Young SNRs

  4. Non-resonant Bell instability: E-max ISM ρ= cost WIND ραR-2 • Independent from the B field strength • Proportional to CR efficiency (ξCR) • Strong dependence on shock velocity ED phase

  5. Spectrum of escapingparticles Acceleration spectrum Caprioli et al. 2010, Schure&Bell 2013 STARTING POINT WIND ρejαR-k k=[7,9] No sharp cut-off above EM! p=[3,4]

  6. Observedspectrum Observed Spectrum Spallation Diffusion Fixed Variables Mej= 1 M ESN= Supernova energy dM/dt= 10-5M/yrs R = Explosion rate Vw= 10 km/s Rd= 10 kpc ξCR H= 3 kpc nd= 1 cm-3kpc EM t0 V0 D0= 3 x 1028 cm2 s-1 δ= 0.65 σsp= α(E) Αβ(E)

  7. Standard energetics: k=7 ESN= 1051 erg R= 1/30 yrs EM= 6.6 x 1014 eV ξCR= 12% t0= 96 yrs v0=10.445 km/s

  8. Standard energetics: k=8 ESN= 1051 erg R= 1/30 yrs EM= 6.4 x 1014 eV ξCR= 10 % t0= 88 yrs v0=11.339 km/s

  9. Standard energetics: k=9 ESN= 1051 erg R= 1/30 yrs EM= 6.3 x 1014 eV ξCR= 8.5 % t0= 84.5 yrs v0=11.830 km/s

  10. Time problem ~2x1012 ~3x1015 • τdyn> τpp≅ 103 s • τdyn> τIC≅ 106 s • τdyn> τph≅ 109s

  11. KASKADE Grande (Apel,2013) k=9 ESN= 1052 erg R= 1/950 yrs EM≅ 9.4 x 1015eV ξCR≅13 % t0≅27 yrs v0 ≅37.500 km/s

  12. KASKADE Grande + ARGO (Di Sciascio, 2014) k=9 ESN= 1052 erg R= 1/950 yrs EM≅ 9.4 x 1015eV ξCR≅13 % t0≅27 yrs v0 ≅37.500 km/s

  13. ARGO k=9 ESN= 1051 erg R= 1/30 yrs EM≅ 6.3 x 1014eV ξCR≅8.5 % t0≅84 yrs v0 ≅11.800 km/s

  14. ARGO (Di Sciascio, 2014) k=9 ESN= 4 x 1051 erg R= 1/60 yrs Uncertainty on the data? Additional component? EM≅ 1.2 x 1015eV ξCR≅4.5 % t0≅42 yrs v0 ≅23.700 km/s

  15. Conclusions • Bell non-resonant instability (NRI) predicts that very energetic SNRs can reach PeV energies • Our toy-model shows that the NRI leads to the release of a steep power-law spectrum in the ejecta dominated phase • The “knee” provided by our model is at E < 3x1015eV for standard energetics • KASKADE Grande data can be fitted only by requiring a challengingly large energetics of a SNR • Our model can fit ARGO data of the light component but a fit to the overall spectrum requires the existence of another population of very energetic particles in addition to the SNR one.

  16. Thankyou verymuch!

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