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The r-Process in the High-Entropy-Wind of Type II SNe

The r-Process in the High-Entropy-Wind of Type II SNe. K. Farouqi Inst. für Kernchemie Univ. Mainz, Germany Frontiers Workshop August 20-22 2005. The High-Entropy-Wind Site. r-process. For a given blob of matter behind the shock front above the proto-neutron star :

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The r-Process in the High-Entropy-Wind of Type II SNe

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  1. The r-Process in the High-Entropy-Wind of Type II SNe K. Farouqi Inst. für Kernchemie Univ. Mainz, Germany Frontiers Workshop August 20-22 2005

  2. The High-Entropy-Wind Site r-process

  3. For a given blob of matter behind the shock front above the proto-neutron star : define three parameters: • Electron abundance: Ye=Yp=1-Yn (p/n-ratio) Example: Ye=0.45  55% neutrons & 45% protons • Radiation entropy: Srad~ T3/ρ ( nn) • Expansion speed Vexpwhich determines the process durations  and r : Example: Vexp= 7500 km/s, R0= 130 km  = 35 ms, r=280 ms

  4. The -process • NSE: All nuclear reactions via strong and electro-magnetic interactions are very fast when compared with dynamical timescales. At T9≈ 6, -particles become the dominant constituent of the hot bubble! Recombination of the -particles is possible via: • 3→ 12C and • ++n → 9Be, followed by 9Be(,n) 12C • Charged-particle freeze-out at T9≈ 3 with: • Dominant part of -particles ~ 80% • Some heavy nuclei beyond iron (80 <A< 110) • Probably a little bit of free neutrons  Seed composition for a subsequent r-process.

  5. Seed nuclei after an -richfreeze-outS=200, Vexp=7500 km/s • Neutron-rich seed beyond N=50 • difference to „classical“ r-process with 56Fe seed • avoids N=50 r-process bottle-neck •  seed nuclei: 94Kr, 100Sr (87Se, 103Y, 89Br, 84Ge, 95Kr, 76Ni, 95Rb below 5%)

  6. Parameter combinations allowing a subsequent r-process (1<Yn/Yseed<150) r-process „strength“ formula:

  7. Synthesizing the A=130 peak S=196 Process duration: 146 ms

  8. Synthesizing the A=195 peak S=261 Process duration: 327 ms not yet enough Pb Th U

  9. Synthesizing the Th, U region S=280 Process duration: 463 ms Pb Th U

  10. Synthesizing the A=130 and A=195 peaks plus the Th, U region S=196 + 261 + 280 Superposition of individual S-components Pb Th U

  11. Superposition of 6 entropy sequences to reproduce the total solar r-process pattern(70< A <240) A=130 (N=82) shell A=195 (N=126) shell Th, U r-process chronometers 14 Gyr

  12. Neuton capture rates Dynamic r-process network calculations for the high-entropy wind scenario of SNII temperature-dependent <sn> from NON-SMOKER (T. Rauscher) Due to still“fast“ freeze-out, no significant effect of <sn> up to the A≈130 peak region ! Abundance Y However, for A>140 (REE,third peak, Th-U) S>250 components freeze-out slower ↷ late neutron capture can modify the final r-abundance pattern  Ye= 0.45 S = 195 Massnumber

  13. The role of β-delayed neutrons in the r-process at A=130 and 195 red: no re-captured β-delayed neutrons blue: β-delayed neutrons re-captured red: no β-delayed neutrons emitted  „progenitor“ abundances blue: β-delayed neutrons emitted and re-captured

  14. Summary • Conditions for successfull r-process • (even for Ye=0.49!) • „strength“ formula Yn/Yseed=f(S,Ye,Vexp) • Due to improved nunclear-physics input •  max. S=280 (for Ye=0.45) • Total process duration up to Th, U •  tr=465 ms • leaves time for fission recycling • Freeze-out effects (late non-equilibrium phase) •  negligible up to A=130 peak • important for REE „pygmy“ peak and A=195 peak

  15. Outlook • Needed : - more experimental nuclear-physics data - better global theoretical models for: nuclear masses, gross b-decay properties neutron-capture rates,fission properties,…. • Neutrino effects • Inclusion of r-process network into 3D hydro-dynamical SN simulations.

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