1. 1/15 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. 2/15 The High-Entropy-Wind Site r-process

3. 3/15 For a given blob of matter behind the shock front above the proto-neutron star : define three parameters: Electron abundance: Y e =Y p =1-Y n (p/n-ratio) Example: Y e =0.45  55% neutrons & 45% protons Radiation entropy: S rad ~ T 3 /ρ (  n n ) Expansion speed V exp which determines the process durations   and  r : Example: V exp = 7500 km/s, R 0 = 130 km    = 35 ms,  r = 280 ms

4. 4/15 The  -process NSE: All nuclear reactions via strong and electro-magnetic interactions are very fast when compared with dynamical timescales. At T 9 ≈ 6,  -particles become the dominant constituent of the hot bubble! Recombination of the  -particles is possible via: 1.3  → 12 C and 2.  +  +n → 9 Be, followed by 9 Be( ,n) 12 C Charged-particle freeze-out at T 9 ≈ 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. 5/15 Seed nuclei after an  -rich freeze-out S=200, V exp =7500 km/s Neutron-rich seed beyond N=50  difference to „classical“ r-process with 56 Fe seed  avoids N=50 r-process bottle-neck  seed nuclei: 94 Kr, 100 Sr ( 87 Se, 103 Y, 89 Br, 84 Ge, 95 Kr, 76 Ni, 95 Rb below 5%)

6. 6/15 Parameter combinations allowing a subsequent r-process r-process „strength“ formula: (1<Y n /Y seed <150)

7. 7/15 Synthesizing the A=130 peak S=196 Process duration: 146 ms YeYe Entropy S r-processduration  [ms] n n [cm -3 ] at freeze-out T 9 [10 9 K] at freeze-out 0,492302341,9 x10 20 0,53 0,451901468,1 x10 21 0,79 0,411601099,0 x10 21 0,77

8. 8/15 S=261 Pb Th U not yet enough Process duration: 327 ms YeYe Entropy S r-processduration  [ms] n n [cm -3 ] at freeze-out T 9 [10 9 K] at freeze-out 0,492904122,0 x10 21 0,33 0,452603271,5 x10 22 0,41 2352132,9 x10 22 0,42 Synthesizing the A=195 peak

9. 9/15 Synthesizing the Th, U region S=280 Pb Th U Process duration: 463 ms

10. 10/15 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. 11/15 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. 12/15 Abundance Y Massnumber Neuton capture rates temperature-dependent from NON-SMOKER (T. Rauscher) Dynamic r-process network calculations for the high-entropy wind scenario of SNII Due to still “fast“ freeze-out, no significant effect of up to the A≈130 peak region !  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 Y e = 0.45 S = 195

13. 13/15 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. 14/15 Summary Conditions for successfull r-process (even for Y e =0.49!)  „strength“ formula Y n /Y seed =f(S,Y e,V exp ) Due to improved nunclear-physics input  max. S=280 (for Y e =0.45) Total process duration up to Th, U   r =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. 15/15 Outlook Needed : - more experimental nuclear-physics data - better global theoretical models for: nuclear masses, gross  -decay properties neutron-capture rates,fission properties,…. Neutrino effects Inclusion of r-process network into 3D hydro- dynamical SN simulations.