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Sintesi di elementi leggeri in stelle di ramo asintotico

Sintesi di elementi leggeri in stelle di ramo asintotico. S. CRISTALLO (1) O. Straniero (1) R. Gallino (2) L. Piersanti (1). (1) Osservatorio di TERAMO , INAF (2) Universita’ di Torino. s -process ( AGB Stars). r -process ( SuperNovae). p -process (proton-rich nuclei).

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Sintesi di elementi leggeri in stelle di ramo asintotico

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  1. Sintesi di elementi leggeriin stelle di ramo asintotico S. CRISTALLO(1) O. Straniero (1) R. Gallino(2) L. Piersanti (1) (1) Osservatorio di TERAMO, INAF (2) Universita’ di Torino

  2. s-process (AGB Stars) r-process (SuperNovae) p-process (proton-rich nuclei)

  3. THE AGB PHASE 1: THE SCHEME

  4. STARTING PARAMETERS but.... Z = Z [Fe/H]=0  • Calibration of the SSM (Standard Solar Model) with • the new composition • New determination of solar C, N and O • (Allende-Prieto et al. 2002, Asplund et al. 2004): Z/X=0.0176 Zini  0.015 Heini= 0.27 αmixing length = 1.9

  5. REF: Freytag (1996), Herwig (1997), Chieffi (2001), Cristallo (2001,2004) How we treat the convection • Schwarschild criterion:to determine convective borders • Mixing length teory:to calculate the element velocities inside the convective zones v = vbce · exp (-d/βHp) where: • Vbceis the convective velocity at the inner border of the convective envelope (CE) • d is the distance from the CE • Hp is the scale pressure height • β= 0.1 • At the boundaries we assume that • the velocity profile drops, following • an exponentially decaying law WARNING: vbce=0 except during Dredge Up episodes • Efficiency of the mixing:we take it proportional to the ratio between the convective • time scaleand the time step of the calculation (Spark & Endal 1980)

  6. Reactions Reference (n,γ) (n,p) and (n,α) p and a captures beta decay Bao & Kaeppeler Koehler,Wagemans NACRE Takahashi&Yokoi THE NETWORK About 500 isotopes More than 700 reactions fully coupled with the physic evolution

  7. Some examples… LEGENDA: Around 26Al The bottlenecks

  8. M=2M Z=Z THE AGB PHASE 2: THE MODEL First formation of the 13C-pocket ACTIVATION OF THE 13C(α,n)16O reaction

  9. Formation of the 13C-pocket after a Pulse with Third Dredge Up 12C 13C 22Ne 14N 23Na H

  10. Variation of the 13C-pocket pulse by pulse X(13Ceff)=X(13C)-X(14N)

  11. The 13C(α,n)16O reaction • Efficient in radiative conditions in the He-intershell at stellar low energies • Very difficult to measure it due to the presence of a sub-treshold resonance REFERENCES: • Caughlan&Fowler (1988) • Drotleff et al. (1993) • Angulo et al. (1999) • Kubono et al. (2003) At T8=1: differences by a factor of 4!!!!

  12. Final surface elements distribution 13C(α,n)16O from Drotleff et al. (1993) 0.1 deX (maximum) using Kubono (2003) and NACRE (1999)

  13. Production of 15N and 19F M=2M Z=10-4 13C 14N 19F 15N H

  14. 15N(p,α)12C Rate divided by2 18O(p,α)15N Rate multiplied by 2 Experimental data at low energies from: Redder et al. 1982 Zyskind et al. 1979 About 50 resonances between 20 and 6746 KeV TESTS (better EXCERCIZES...): 15N(n,γ)16N 14N(n,γ)15N 14C(n,γ)15C 14C(α,γ)18O Rate divided by 2 14C(p,γ)15N

  15. He-intershell abundances at the end of the following Thermal Pulse -20% +20%

  16. M=2M Z=10-4 13C 26Al 60Fe 41Ca H RADIACTIVE ISOTOPES

  17. (40Ca/ 41Ca)equilibrium M=2M Z=Z

  18. The 14N(n,p)14C reaction Our choice (ST): Koehler, P.E. & O’Brien, H.A. (1989, Phys. Rev C 39, 1655) EXERCIZES ST x 2 ST / 2

  19. Low M - Low Z AGB: M=1.5 Z=5x10-5 Y=0.24 Convective envelope CNO He 13C(a,n) CO-core 3a->12C (Straniero et al. 2005)

  20. H He 1 4 3 2 See also: Hollowell, Iben & Fujimoto 1990 Fujimoto, Ikeda & Iben 2000 Iwamoto et al. 2004

  21. Production of 15N and 19F M=1.5M Z=5x10-5 13C 14N 19F 15N H

  22. M=1.5M Z=5x10-5 Envelope composition 12C/13C 14N/15N C/O Sergio Cristallo: Il C12/C13 scende perche’ e’ la concentrazione di equilibrio del bruciamento di H convettivo Il C/O al secondo pulso scende perche’ porta su O, mentre C e’ gia’ enhanced N14/N15 scende perche’ il pulso successivo non e’ riuscito a bruciare il amre di N15 che si era formato. Mentre l’N14 e’ tutto bruciato.

  23. Production of heavy elements (s-process) M=1.5M Z=5x10-5 13C 14N 139La 89Y H 208Pb

  24. M=1.5M Z=5x10-5

  25. THE NATIONAL RESEARCH COUNCIL COMMITTEE ON PHYSICS (Febbraio 2002) 1.  What is dark matter? 2.  What is dark energy? 3.  How were the heavy elements from iron to uranium made? 4.  Do neutrinos have mass? 5.  Where do ultra-energy particles come from? 6.  Is a new theory of light and matter needed to explain what happens at very high energies and temperatures? 7.  Are there new states of matter at ultrahigh temperatures and densities? 8.  Are protons unstable? 9.  What is gravity? 10.  Are there additional dimensions? 11.  How did the Universe begin? What about elements from idrogen to iron???

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