How many r- (or s) -process components in very metal-poor stars ?

1. How many r- (or s)-process componentsin very metal-poor stars? R. Gallino(1), S. Bisterzo(1), O. Straniero(2), S. Cristallo(2), I. I. Ivans (3,4), W. Aoki(5), T. Beers(6) (1) Dip. Fisica Generale, Universita' di Torino (Italy) (2) Osservatorio Astronomico di Collurania - INAF, Teramo, (Italy) (3)The Observatories of the Carnegie Institution of Washington, Pasadena, CA, (USA) (4)Princeton University Observatory, Princeton, NJ (USA) (5)National Observatory Tokyo, Dept. of Astronomy (Japan) (6)University of Michigan MI (USA)

2. OUTLINE • The classical analysis of the s-process is commonly used to predict the s-percentage isotope contributions to the solar system, as well as to the solar r-process residuals (calculated as r = 1 - s). • Three s-process components were anticipated by the classical analysis: the weak, the main, and the strong s-component • This first-order prediction still remains valid for close-by nuclides. However the main s-component is far from being a unique process! • Comparison of AGB stellar model calculations at various metallicitieswith spectroscopic observations of different stellar populations clearly demonstrates the vaste multiplicity of s-process components. • Major evidence is provided by low-metallicity C-rich and s-process rich/poor stars.

3. Short-lived isotopes in the Early Solar System and a multiplicity of r-process components • Observations of short-lived r-process isotopes in the early solar system help to characterize at least three different r-process components. • The two short-lived isotopes: 129I (t = 23 Myr) and 182Hf (t = 13 Myr), which are most of r-process origin, have been shown to be alive in the early solar system with a ratio incompatible with a unique r-process distribution. (Wasserburg et al. 1996, ApJ 466, 109). Observations of ultra metal-poor and r-process enriched stars agree (and gives new constraints) with the above conclusion from meteoritic studies.

4. The third r-process component from meteoritic studies • A further conflict exists from the analysis of the actinides 244Pu (t = 115 Myr) , and new upper limits on 247Cm (t = 22.5 Myr) in the Early Solar System. (Wasserburg et al. 2005, Nucl. Phys. A, in press). • Recent spectroscopic analyses of r-process-rich UMP stars of the ratio Th/Eu, or Pb/Eu, point out the necessity of a breakdown of the idea of a unique heavy r-process distribution beyond Ba. However this is still debated. • New observations of r-rich VMP (Ivans; Honda) indicate various degrees of light-r and heavy-r mixtures

5. Ce

6. The Sr, Y and Zr puzzle: how many n-capture components? [Sr/Fe], [Y/Fe] and [Zr/Fe] vs [Fe/H] Travaglio et al., ApJ 601, 864 (2004).

7. [Ba/Fe], [Eu/Fe] and [Ba/Eu] vs [Fe/H] Travaglio et al., ApJ 521, 691 1999

8. The first intrinsic indicator [hs/ls] ≈ Busso et al. 2001 ApJ 557, 802

9. Busso, Gallino, Wasserburg ARAA 1999

10. NOTE: Initial Mass are estimates dependent alsoon mass loss rates adopted [Pb/Fe] vs [Fe/H] envelope last pulse condition M ≈ 1.5 Msun

11. The second intrinsic indicator [Pb/hs] Lucatello PhD Thesis M ≈ 1.5 Msun

12. Vanhala and Cameron (1998) showed through numerical simulations how the supernova ejecta may interact with a nearby molecular cloud, polluting it with fresh nucleosynthesized material and triggering the condensation of binary system of low mass. Note that according to Lucatello et al. (2005) all C-rich and s-rich metal-poor stars show binarity from their radial velocity temporal variations. The subsequent evolution of such close binary systems, and how the pre-enrichment of r-process elements influences the s-process occurring in the more massive AGB companion is discussed and compared with a dozen of very-low metallicity lead stars, s and r process rich.

13. CS29497-030 predictions updated

14. The Sr, Y, Zr problem and choice of the initial mass M = 1.3 Msun M = 1.5 Msun

15. M = 1.5 Msun M = 1.3 Msun

16. M = 1.3 Msun M = 1.5 Msun

17. Spectroscopic Na (and Mg)  Second indicator of the parent AGB Stellar Mass In Fig 4 we show the results of AGB models of M = 1.3, 1.5, 2, 3, and 5 Msun, for the same 13C-pocket, at [Fe/H] = – 2.60. A strong primary production of 22Ne results in advanced pulses, by conversion of primary 12C to 14N in the H-burning ashes, followed by 2a captures on 14N in the thermal pulses and implies a primary production of 23Na via 22Ne(n,g)23Na, (and 23Na(n,g)24Na(b-)24Mg). Case ST [Fe/H] = -2.60 AGB models Fig. 4

18. C-rich and no s-rich AGB stars Case of M = 1.2 Msun and ST/75 ls hs Pb

19. Case of M = 1.3 Msun and ST/75 ls hs Pb

20. Case of M = 1.5 Msun and ST/75 ls hs Pb

21. NEW FRANEC: Time dependent treatment of convection • velocity profile v = vbc · exp (-d/f Hp) CONVECTIVE ZONES BOTTOM CONVECTIVE BORDER • Schwarzschild criterion • Mixing length theory Network extended up to Bi, fully coupled with the evolutionary code

22. The Third Dredge Up (TDU) starts occurring at MH ~ 0.58 Msun and is more efficient. • The TDU ceases when M(envelope) < ~ 0.3 Msun.

23. M = 1.5 Msun, Z = 5.10-5 Bottom Convective envelope First Huge TDU HCNO Straniero et al. Mem. Soc. Astron. It. 75 665 (2004) 13C(a,n)16O 3a12C

24. Straniero et al. Mem. Soc. Astron. It. 75 665 (2004) Suda et al. 2004; OMEG05 Picardi et al. 2004. Weiss et al 2003

25. H-burning He-burning 22Ne(a,n) 13C(a,n) 12C H Formation of 13C and 14N 13C 14N Physics and Chemistry at the H-ingestion 1042 erg/s !!!!!!

27. Self consistent formation of the 13C-pocket using the velocity profile algorithm

28. 2th TDU episode 1th TDU episode: Strong neutron flux, but too short timescale Envelope enrichment

29. Pb, Bi Hf, Ta, W, All together 2th TDU episode Cd, Pd, Sn Ba group 1th TDU episode: Strong neutron flux, but too short timescale Sr, Y, Zr Envelope enrichment Eu

30. The Huge TDU mixes with the envelope a huge amount of 13C

31. Light elements F Ne N Na C Mg Al O

32. The La to Eu ratio in metal-poor AGB stars AGB of M = 1.3 Msun, [Fe/H] = -2.60

35. Live 26Al in early solar system condensates Lee, Papanastassiou, Wasserburg, ApJ 211, L107 (1976)