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18-19 Settembre 2006 Dottorato in Astronomia Università di Bologna

18-19 Settembre 2006 Dottorato in Astronomia Università di Bologna. The Virial Theorem. Non-degenerate. log P. r 4/3. relativistic. M 2. M 1. r 5/3. Non-relativistic. log r. Degenerate Fermi gas. Collapse or ignition. Stellar core evolution. M<0.8 M ¤ 0.8<M/M ¤ <8 8<M/M ¤ <11

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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. The Virial Theorem

  3. Non-degenerate log P r4/3 relativistic M2 M1 r5/3 Non-relativistic log r Degenerate Fermi gas Collapse or ignition Stellar core evolution

  4. M<0.8 M¤ 0.8<M/M¤<8 8<M/M¤<11 11<M/M¤<100 M>100 M¤ t>1/HO 15 Gyr<t<30 Myr 0.5<Mf /M¤<1.1 CO WD Thermonuclear SNe Progenitors t.10-30 Myr Mf =1.2-1.3 M¤ ONeMg WD T<10 Myr Mf =1.2-2.5 M¤ Fe (Ye.0.45) collapse NS or BH Core Collapse SNe Progenitors T = few Myr O (pair jnstability) (Ye=0.5) may or may not explode Stellar evolution

  5. Summary: • Age of simple (stellar clusters) and complex (disk, bulge, halo) stellar populations. • Properties of nowadays extinct stellar populations. • Nature of barionic dark matter • Physics of high density matter • Amount of C/O in the He-exhausted core: hints for nuclear physics and theory of turbulent convection, as well as constraints for massive stars evolution and any type of SNe

  6. 47 tuc (Zoccali et al 2001)

  7. M4 (Bedin et al. 2001)

  8. NGC 6397 (King et al. 1998)

  9. M4: the deepest WD cooling sequence Data obtained with the WFPC2on board the HST(Hansen et al. 2002, Richer et al. 2002). The target is a region located 5’ E of the center of M4 and has been imaged through the: F606W(98 orbits x 1300 sec) F814W (148 orbits x 1300 sec) 12.7"0.7 Gyr.

  10. Cooling sequence

  11. Crystallization phase Convective coupling Debye cooling Age from luminosity functions WD cooling Different colors > different WD masses

  12. WD Age from the CM-diagram:Collision Induced Abortion (CIA) and the blue hock Isochrones for DA WD

  13. Simulated WD sequence in NGC6397 with ACS

  14. NGC 6397

  15. The observed WD Luminosity function Goodmatch between theory and observation Gooddescription of the high density matter behavior Bad: only a lower limit for the age can be set: 9 Gyr Good: smaller dependence on the distance

  16. WDs are relicts of an extinct population: progenitors mass function: Synthetic NGC 6397 13 Gyr - Salpeter mass function

  17. DA White Dwarf e- highly degenerate isothermal core C-O ions main energy reservoir e- non-degenerate envelope thermal insulator 98% C-O core (0.5-1.1 MÀ) 2% He mantel (<10-2 MÀ) 0.01% H envelope (<10-4 MÀ) no conduction

  18. Thermal conductivity by degenerate electrons He-rich Mantel C/O Core From Prada Moroni & Straniero 2002

  19. WD progenitors • Case B no-AGB • Case B1 Post-AGB with final thermal pulse • Case B2 classical Post-AGB • Case C Post RGB

  20. He-burning: the competition between 3a->12C and 12C+a->16O+g 4He 12C 16O 5 M Z=0.02 Y=0.28

  21. Jp Ex (keV) ECM (keV) 10957 0- 10367 4+ 3195 2685 2+ 9847 9580 1- 2418 8872 2- Q = 7.162 MeV Gamow peack energies 7117 1- 12C+4He 6917 2+ -45 -245 6130 3- 0+ 6049 0 0+ 16O level scheme Na<s,v> (10-15 cm3mol-1s-1) for T9=0.2

  22. High rate 12C(a,g)16O Low rate White Dwarf interior: C and O profiles

  23. low rate high rate cooling is affected by the internal chemical stratification

  24. 4 models for convection • same nuclear reaction rates • different convective scheme

  25. 16O MD WD internal composition is affected by core He burning convection

  26. At the onset of the core collapse • e-+p à n+ne (10 MeV) • 56Fe+g à 13a+4n (124 MeV)

  27. SNe Ia:TheoreticalLight Curves

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