The Re/Os Clock, astration and C-burning in massive stars

1. The Re/Os Clock, astration and C-burning in massive stars Roberto Gallino Dipartimento di Fisica Generale, Università di Torino Collaboration with Marita Mosconi, Franz Kaeppeler, Alberto Mengoni, Marco Pignatari, Oscar Straniero, Sara Bisterzo

2. Outline • Re/Os Clock • C-burning in massive stars

3. 188Re 186Re 16.98h 89.25h 187W 185W 23.7h 75.1d

4. Mosconi et al. (2007), PrPNP59, 165–173

5. Mosconi et al. (2007), PrPNP59, 165–173

6. During the s-process

8. The weak s proces component in MASSIVE STARS Most of the s elements between iron andstrontium (60 <A <90) are produced in massive stars (with initial mass M > 8 Mo), forming theweak s component (Käppeler et al. 1989; Beer et al. 1992, and references therein). Then, what’s the impact on the Re/Os clock????

9. The main neutron sourceIN MASSIVE STARS • is the 22Ne(a,n)25Mg reaction, activated: • at the end ofthe convective He-burning core (Peters 1968; Couch et al. 1974; Lamb et al. 1977) • and in thefollowing convective C-burning shell (e.g., Raiteri et al. 1991a), reactivated during C-burning, where thea-particles required to produce neutrons are provided by the 12C(12C,a)20Ne reaction (e.g., Arnett& Truran 1969) • The s nucleosynthesis occurs both during convective core He burning and during convective Cshell burning. The neutron exposuresare comparable. • Stellar models providing the evolution of the star up to the finalphases and the supernova explosion confirm this scenario (e.g. Woosley & Weaver 1995; Limongiet al. 2000; Woosley et al. 2002; The et al. 2007).

10. The weak s-component: summary Convective Convective Core He-burning Shell C-burning Peak neutron density (1011- 1012 n/cm3) T~ 1-1.4 109 K The convective shell works over the ashes of the core He-burning Low neutron density (~106 n/cm3) T~3-3.5 108 K Classical s-process The final weak s component is an overposition of two different s(sr) components

11. Cu Post-SN (yields) Explosive Ne-burning 2.8 < MΘ < 3.5 Convective Shell C-burning 3.5 < MΘ < 5.8 Convective He-burning 5.8 < MΘ < 6.7 He-shell 6.7 < MΘ < 9.0 Convective C shell burning Explosive nucleosynthesis He burning Core Shell H envelope Factor = 200 M=25 Msun, Z=Zsun (Nucl. Data Page, A. Heger)

12. New high-resolution spectroscopy results r-rich stars BD+173248 HD 155444 CS 22892-052 Primary contribution Secondary-like contribution SNIa contribution to Fe

13. Nucl. Phys, 1998

14. Rauscher et al. 2002, ApJ, 576, 323

15. Rauscher et al. 2002, ApJ, 576, 323

18. CONCLUSION • The answer is: • During the main s-process in low mass AGB stars, • there is a 10% contribution to solar 187Re by the main component (non accounted for e.g., by Hayakawa et al. 2008). This means no astration by “destruction” of 187Re by low mass stars • during the s-process in massive stars • the 187Re is destroyed, but is almost restaured by the radiogenic contribution from 177W ! • Consequently, the astration effect both in massive stars and in low mass stars (Takahashi’s struggle) has no effect. This makes the Re-Os chronometer • on firmer grounds.

22. 192 184 190 189 188 186 187 186 187 184

23. Models: Hydrostatic nucleosynthesis in massive stars • Post-processing models follow: Convective core He-burning and Convective shell C-burning (Raiteri et al. 1991, 1993) • Updated network Bao et al. 2000 for (n,γ) + more recent measures, or theoretical expectations (KADoNiS, I. Dillmann), β decay rates from various sources, (n,p) and (n,α) channels....

24. He core: 22Ne (secondary-like) is the neutron source 25Mg (secondary-like) is the main neutron poison → constant neutron exposure at different metallicities constant number of neutrons captured per iron seed nc = Σ56209(A-56)[Nfin(A)-Nin(A)]/56Feini → S-PROCESS YIELDS BEYOND IRON SCALES WITH THE METALLICITY

25. Kippenhahn’s Diagram for a star with M= 25 M(sun) and solar metallicity (Limongi & Chieffi 2000, ApJS)

26. Kippenhahn’s Diagram for a star with M= 25 M(sun) and solar metallicity (Limongi & Chieffi 2000, ApJS)

27. Principal isotopes (pre-supernova): 4He 16O 12C 20Ne 1H 12C 28Si 4He M=25 Msun, Z=Zsun (Nucl. Data Page, A. Heger)

28. In the C shell: C-burning: 12C(12C,α)20Ne, α-source ((α,n) channels are activated!) 12C(12C,p)23Na, p-source 12C(12C,n)23Mg*, negligible 16O is the most abundant isotope (~ 0.7)

29. In the C Shell: Possible neutron sources: 13C(α,n)16O 17O(α,n)20Ne 18O(α,n)21Ne 21Ne(α,n)24Mg 22Ne(α,n)25Mg 25Mg(α,n)28Si 26Mg(α,n)29Si

30. The weak s-component: summary Convective Convective Core He-burning Shell C-burning Low neutron density (~106 n/cm3) T~3-3.5 108 K Classical s-process See Lamb et al. 1977, Couch et al. 1974, Prantzos et al. 1987, Raiteri et al. 1991 ...... Peak neutron density (1011- 1012 n/cm3) T~ 1 109 K The convective shell works over the ashes of the core He-burning (Raiteri et al. 1991) The final weak s component is an overposition of two different s(s+) components

32. Galactic chemical evolution (GCE)

33. Startingfrom GCE calculations, Travaglio et al. (2004a) showed that the weak s component and the mains component do not fully reproduce the s abundances between strontium and barium, proposingthe existence of a new unknown component called lighter element primary process (LEPP).

34. Farouqi et al. (2009), ApJ 694, 49

39. Timmes, Woosley & Weaver 1995, ApJS