1. White Dwarfs in Globular Clusters O. Straniero, P. Prada Moroni, I. Dominguez, G. Imbriani, L. Piersanti G. De Marchi P. Bergeron

2. 47 tuc (Zoccali et al 2001)

3. M4 (Bedin et al. 2001)

4. NGC 6397 (King et al. 1998)

5. Data obtained with the WFPC2 on 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 x 1300 sec) F814W (148 x 1300 sec) M4: the deepest WD cooling sequence 12.7 " 0.7 Gyr.

6. WD Age from the CM-diagram: CIA connection

7. Age from luminosity function Crystallization phase Debye cooling Convective coupling WD cooling

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

9. Expected WD sequence in NGC6397 with ACS

10. WD mass and progenitor mass function Synthetic NGC 6397 13 Gyr - Salpeter mass function

11. 98% C-O core 2% He mantel (<10 -2 M À ) 0.01% H envelope (<10 -4 M À ) no conduction e - highly degenerateisothermal envelope core energy reservoir C-O ions main energy reservoir e - non-degenerate thermal insulator DA White Dwarf

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

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

14. 4 He 16 O 12 C 5 M  Z=0.02 Y=0.28 He-burning: the competition between 3  -> 12 C and 12 C+  -> 16 O+ 

15. E x (keV) JJ 10957 10367 9847 9580 8872 7117 6917 6130 6049 0 0-0- 4+4+ 2+2+ 1-1- 2-2- 1-1- 2+2+ 3-3- 0+0+ 0+0+ 12 C+ 4 He 2418 2685 3195 E CM (keV) Gamow peack energies -45 -245 16 O 16 O level scheme Q = 7.162 MeV LowAdop.high Kunz et al 2001 5.257.5810.2 Buchman n 1996 3.047.0413.04 NACRE 5.449.1112.8 CF88 4.74 CF85 11.3 N a (10 -15 cm 3 mol -1 s -1 ) for T 9 =0.2

16. White Dwarf interior: C and O profiles 12 C(  ) 16 O High rate Low rate

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

18. Core He-burning: the connection between Nuclear Reaction & Convection He (low  ) -> C/O (high  ) C/OHe induced overshooting (Castellani Giannone Renzini 1971) convectiveradiative

19. Semiconvection Convective Core Semi convective Zone Radiative Zone CCSCZRZ

20. Mechanical overshooting a>0 v … 0 a<0 v … 0 a<0 v=0 R CC +  H p  =1

21. 4 models for convection same nuclear reaction rates different convective scheme

22. WD internal composition is affected by core He burning convection MDMD 16 O