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18-19 Settembre 2006 Dottorato in Astronomia Università di Bologna

18-19 Settembre 2006 Dottorato in Astronomia Università di Bologna. ?. Stellar models: basic ingredients. Hydrostatic equilibrium. Mass continuity. Energy transport. Energy conservation. Chemical evolution. p+p D+e + + n D+p 3 He+ g. 3 He+ 3 He 4 He+2p.

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18-19 Settembre 2006 Dottorato in Astronomia Università di Bologna

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  1. 18-19 Settembre 2006 Dottorato in Astronomia Università di Bologna

  2. ?

  3. Stellar models: basic ingredients Hydrostatic equilibrium Masscontinuity Energy transport Energy conservation Chemical evolution

  4. p+p D+e++n D+p 3He+g 3He+3He 4He+2p 3He+4He 7Be+g 7Be+p 8B+g 8B 8Be+e++n 8Be 4He+4He 7Be+e-7Li+n 7Li+p 4He+4He An example: the pp chain

  5. CNO cycle

  6. Moka Express 1933

  7. 5 MO 1 MO Theory and its observational counterpart

  8. 3-a + CNO 3-a CNO pp-chain Globular Clusters

  9. NOVAE RGB-AGB MS 14N(p,g)15O@LUNA

  10. Io IAU general assembly. Chi sono H&R?

  11. Standard CF88 S 14,1 /5 S 14,1 x5 14N(p,g)15O and the GC ages

  12. Base of the convective envelope H-burning shell Depth of the convective envelopeas a function of time 1M Z=0.02

  13. Globular Clusters luminosity function From: Rood et al 1999 ApJ 523, 572

  14. 1 M: chemical profiles 3He-red 4He-blue H-black

  15. Salted envelope C-red N-blue O-black

  16. Low mass stars synthesis 3He crisis Clue for extramix ?

  17. He ignition in degenerate core The high density developed near the center induces the production of thermal neutrinos by plasma Oscillations and the maximum temperature move off center

  18. He-flashes

  19. 4He 3a12C 12C+a 16O+g 12C 16O Central He-burning 5 M Z=0.02 Y=0.28

  20. Convective envelope 5 M Z=0.02 Y=0.28 H 4He,14N 12C,16O Early-AGB: the second dredge up

  21. Convective envelope H-shell He-shell CO core The onset of the thermal pulses The E-AGB terminates when the H shell re-ignites, while the He shell dies down. When the mass of the intershell region exceeds a certain critical value, the He shell suffers a thermal instability.

  22. H-Burning luminosity He-Burning luminosity Evolution of TP stars: 5 M

  23. Thermal instability & nuclear runaway Temperature evolution in the intershell zone Nuclear energy production in the intershell zone

  24. Third dredge up M p TP 13C pocket TP time Third dredge up and 13C pocket After the thermal pulse the envelope expands and cools down. The H shell becomes inactive and the convective envelope can penetrate the H/He discontinuity, bringing to the surface the ashes of the He burning: 12C and s-elements. 1)Few protons diffuse below the base of the convective envelope, where about 20% of the mass is made of carbon. 2)When the H shell re-ignites, a 13C pocket is produced by the 12C+p reaction. 3) During the interpulse, the temperature in the pocket becomes larger than 90x106 K and neutrons are realized by the 13C+a reaction.

  25. Covective shell generated by a TP in IMS T6>300 up to 1011 neutrons/cm3 Neutron sources: 22Ne(a,n)25Mg CNO 14N CNO-burning 14N(a,g)18F(b+) 18O(a,g)22Ne He-burning PRIMARY

  26. intershell zone during the interpulse in LMS & IMS T6>100 106-107neutrons/cm3 Neutron sources: 13C(a,n)16O Few protons injected into a C-rich zone 12C(p,g)13N(b+) 13C PRIMARY

  27. The formation of the 13C pocket In this model, an exponential decay of the convective velocity has been assumed below the convectively unstable zone. H black 13C red 12C green 14N blue

  28. High rate 12C(a,g)16O Low rate The final fate:White Dwarf interior

  29. BUM!! low rate high rate WD cooling & type Ia supernovae

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