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Acceleration of GCR in stellar winds and the GCR 22 Ne/ 20 Ne source ratio N. Prantzos

Acceleration of GCR in stellar winds and the GCR 22 Ne/ 20 Ne source ratio N. Prantzos ( Institut d’Astrophysique de Paris). Galactic Cosmic Ray Source Composition. Volatiles : elements with high A/Q (mass to charge) favored. Is it solar ? Yes, for most isotopic ratios.

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Acceleration of GCR in stellar winds and the GCR 22 Ne/ 20 Ne source ratio N. Prantzos

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  1. Acceleration of GCR in stellar winds and the GCR 22Ne/20Ne source ratio N. Prantzos (Institutd’Astrophysique de Paris)

  2. Galactic Cosmic Ray Source Composition Volatiles:elements with high A/Q (mass to charge) favored Is it solar ? Yes, for most isotopic ratios Refractories:overabundant, but no clear trend with A/Q No, for elemental ratios  Selection effects Ellison, Meyer, Drury (1997): SN shocks accelerate ISM gas (volatiles) and sputtered grains (refractories) CNO overabundant by ~1.5 to 8 ; Most excess CNO attributed to WR stars After taking into account several selection effects, it seems that the Source composition of GCR today is ~solar. Except for some excess C and Ne22/Ne20 from WR star winds (Cassé and Paul 1982)

  3. Galactic Cosmic Rays : what is the composition of accelerated matter ? A ISM B ISM SN SN FS FS RS Forward Shock accelerates ISM Reverse Shock accelerates SN ejecta D ISM C ISM Wind SN FS SBM C, N, Ne22.. SN Shocks accelerate Superbubble matter Forward Shock accelerates Wind + ISM

  4. A forward shock is launched at MEXP and runs through the wind of the star, enriched with products of H- and/or He- burning, through the unprocessed envelope, and finally in the interstellar medium. ASSUMPTION: Particle acceleration starts in the beginning of the Sedov-Taylor (ST) phase, when MSWEPT ~ MEJEC (BUT: When does it stop ?) Depending on the previous mass loss of the star, acceleration may occur when the shock is still within the wind (more massive stars) or in the ISM (less massive stars), thus affecting the composition of accelerated particles.

  5. Stellar models with mass loss and rotation (Hirschi et al. 2005) or no rotation (Chieffi and Limongi 2006) Ingredients of stellar models (convection, mass loss, rotation etc.) determine the various quantities (MEXP, MREM, MWIND, etc.) Models with rotation have larger amounts of processed material MPROC MASS (M⊙ )

  6. Rotating models have larger yields of He-burning products (C-12, Ne-22, etc.) in their winds MASS (M⊙ )

  7. Stellar models with mass loss and rotation (Hirschi et al. 2005) Integrated mass swept up by the forward shock, as it moves outwards

  8. The circumstellar environment of mass losing stars Fast rotating Z=0.001 20 M⊙ (van Marle et al. 2008) (van Marle et al. 2008) For a steady stellar wind, the density profile can be approximated by Density Radius-2 with

  9. Propagation of forward shock into a stellar wind of profile ρ(r) r-2 (Ptuskin and Zirakhasvili 2005, Caprioli 2011)

  10. Caprioli 2011

  11. MIN Particle acceleration starts in beginning of ST and is assumed to stop when the velocity of the shock drops to MIN chosen such as the IMF averaged ratio Ne22/Ne20 of accelerated particles equals the observed one R = (Ne22/Ne20)GCR = 5.3 ⊙ TIME (yr)

  12. The IMF averaged ratio Ne22/Ne20 of accelerated particles equals the observed one R = (Ne22/Ne20)GCR = 5.3 ⊙ for MIN=1900 km/s for rotating models and 2400 km/s for non-rotating ones CL06 HMM05 MASS (M⊙ )

  13. A1: Beginning ST and acceleration The forward shock accelerates particles from a pool of mass MACC = A2 – A1 between the beginning of ST (A1) and =1900 km/s (A2) A2: End acceleration S=1900 km/s Processed material Energy of accelerated particles Mass of accelerated particles Efficiency of acceleration

  14. Are GCR accelerated in Superbubbles ? SN eject at explosion much larger amounts of Ne20 than in their winds but they eject amounts of Ne22 comparable to the ones of their winds The Ne22/Ne20 ratio produced by a stellar generation (averaged over the IMF) should be close to solar (if not: problems with global Nucleosynthesis) In a superbubble, material from the whole IMF should be mixed and accelerated

  15. In a superbubble the time integrated (GCR) Ne22/Ne20 ratio remains compatible with the observed GCR one ONLY for a short early period and ONLY if no original material is left over. Most of the time, and in realistic conditions Ne22/Ne20 is close to solar Superbubbles are NOT at the origin of GCR Ne22/Ne20 nor at the origin of GCR. (Contrary to Higdon et al. 1998, Higdon and Lingenfelter 2003, Binns et al. 2005, 2008)

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