LMS & IMS: their evolution, nucleosynthesis and dusty end

1. LMS & IMS: their evolution, nucleosynthesis and dusty end S. Cristallo in collaboration with Oscar Straniero and Luciano Piersanti Osservatorio Astronomico di Teramo - INAF

2. AGBs: a theoretician perspective Very luminous (103-104 our SUN) Very cold (2000-3000 K)

3. CO Core He-shell H-shell Earth-Sun (~200 RSUN) Earth radius (~10-2 RSUN) Convective Envelope AGB structure Practically, a nut in a 300 mts hot air balloon

4. The s-process in AGB stars 13C(α,n)16O reaction 22Ne(α,n)25Mg reaction TDU TDU HOT BOTTOM BURNING (Boothroyd & Sackmann 1991) Busso et al. 1999

5. Four first-order non-linear constant coefficients differential equations Three characteristic relations HYDROSTATIC, NO ROTATION, NO MAGNETIC FIELDS The FRANEC Code (Frascati RAppson-Newton Evolutionary Code) (Chieffi & Straniero 1989; Straniero et al. 1997; Chieffi et al. 2001; Straniero et al. 2006; Cristallo et al. 2007; Cristallo et al. 2009)

6. Major uncertainty sources in stellar evolutionary codes and their link with grains Opacities; Mass-loss law; Equation of State (IMS); Convection treatment; Non convective mixing mechanisms (LMS).

7. Opacities Atomic opacities Molecular opacities Grains T 4000-5000 K 2000 K C/O>1 C/O<1 CO – C2 – CN - C2H2 – C3 TiO – H2O - CO Marigo 2002; Cristallo et al. 2007

8. C and N enhancements See also: Lederer & Aringer 2009; Weiss & Ferguson 2009 Ventura & Marigo 2009; Marigo & Aringer 2009 Karakas et al. 2010

9. Results The C-enhanced low temperature opacities make the stars redder in the AGB phase Effects on surface temperatures and, therefore, on mass-loss and nucleosynthetic yields

10. FRANEC FRANEC Mass loss law AGB PHASE • BCK - temperature • (Fluks et al. 1994) • Luminosity - MBOL • MK=MBOL-BCK • Period-MK • (Whitelock et al. 2003) • Period – Mass-loss GRAINS DRIVE THE MASS-LOSS Vassiliadis&Wood 1993 Straniero et al. 2006

11. Grains: opacities and mass-loss Winds of carbon stars are considered to be dust-driven winds. Photons lead to a radiative acceleration of grains away from the star. Subsequently, momentum is transferred to the surrounding gas by gas-grains collisions. UNKNOWNS grains opacity (how they interact with radiation); grains growth process; grains nucleation phase (in particular for C/O>>1); stellar pulsation physics. It is commonly assumed that grain sizes are small compared to the relative wavelenght: that’s not always true (see e.g. Mattsson et al. 2011)

12. The Luminosity function of Galactic C-stars Guandalini et al. 2006 (A&A, 445, 1069) Cristallo et al. 2011 (ApJS, 197, 2)

13. The Luminosity function of Galactic C-stars Guandalini & Cristallo, in preparation P-L from Whitelock et al. 2006 Distances from van Leeuwen 2007

14. First attempt (to my knowledge) to evaluate the amount and type of dust production in AGB stars with a stellar evolutionary model Amount of silicates scales with Z Silicates are produced in IMS (strongly dependence on HBB) Mass-loss rate dtermines the dust condensation degree For C-stars, the main source of uncertainty is the amount of dredged up carbon Total mass of dust as a function of the stellar mass Ventura et al. 2012 (MNRAS 424, 2345) Ventura et al. 2012 (MNRAS 420, 1442) Mass of silicates Mass of carbon dust

15. EOS for IMS For Intermediate Mass Stars, the temperature at the bottom of the convective envelope is high enough (T>4e7 K) to allow proton captures: HOT BOTTOM BURNING (Boothroyd & Sackmann 1991)

16. REF: Freytag (1996), Herwig (1997), Chieffi (2001), Straniero (2006), Cristallo (2001,2004,2006,2009) Convection treatment • Schwarzschild criterion:to determine convective borders • Mixing length theory:to calculate velocities inside the convective zones • Mixing efficiency:proportional to the ratio between the convective time scaleand the time step of the calculation (Spark & Endal 1980); • ΔX depends linearly on Δr (NOT diffusive approach). v = vbce · exp (-d/βHp) • Vbceis the convective velocity at the inner border of the convective envelope (CE) • d is the distance from the CE • Hp is the scale pressure height • β= 0.1 At the inner border of the convective envelope, we assume that the velocity profile drops following an exponentially decaying law WARNING: vbce=0 except during Dredge Up episodes

17. Gradients profiles WITH exponentially decaying velocity profile Gradients profiles WITHOUT exponentially decaying velocity profile RADIATIVE He-INTERSHELL CONVECTIVE ENVELOPE During a TDU episode

18. An interesting by-product: the formation of the 13C pocket 13C-pocket 14N-pocket 23Na-pocket

19. Variation of the 13C-pocket pulse by pulse X(13Ceff)=X(13C)-X(14N)*13/14 14N strong neutron poison via 14N(n,p)14C reaction 11th 1st Cristallo et al. 2009

20. 13C pocket and dredge up as a function of b Third TP of 2 Mʘ at Z=Zʘ and Z=10-4

21. Convective 13C burning

22. He-intershell elements enrichments J=Iω=mr2ω Cristallo et al. 2009

23. F.R.U.I.T.Y. (Franec Repository of Updated Isotopic Tables & Yields) August the 9th 2012: added 1.3 MSUN models at all metallicities Z=10-4 models (within the end of November) Dedicated mailing list with upgrades On line at www.oa-teramo.inaf.it/fruity (1.5,2.0,2.5,3.0) MSUN with Z=(1x10-3,3x10-3,6x10-3,8x10-3,1x10e-2,sun,2x10e-2)

24. M=2Mʘ Final AGB composition for 0.0001<Z<Z A key quantity: the neutron/seed ratio, that is n(13Ceff) /n(56Fe) 13C is primary like 56Fe is secondary like

25. s-process indexes (I) [ls/Fe]=([Sr/Fe]+[Y/Fe]+[Zr/Fe])/3 [hs/Fe]=([Ba/Fe]+[La/Fe]+[Nd/Fe] +[Sm/Fe])/4 [ls/Fe] [hs/Fe] [Pb/Fe]

26. Observations vs theory (II): [hs/ls] distributions Ba & CH stars Post-AGB Intrinsic C-rich Intrinsic O-rich Cristallo et al. 2011 [ls/Fe]=([Sr/Fe]+[Y/Fe]+[Zr/Fe])/3 [hs/Fe]=([Ba/Fe]+[La/Fe]+[Nd/Fe] +[Sm/Fe])/4

27. FRUITY Models vs Grains (measurements from Barzyk et al. 2007)

28. FRUITY Models vs Grains (measurements from Barzyk et al. 2007)

29. FRUITY and MONASH models vs Grains (measurements from Avila et al. 2012) The most interesting data are those that do not agree with theoretical models. Ernst Zinner (this morning)

30. A new set of FRANEC rotating AGB models Centrifugal forces lead to deviations from spherical symmetry; Differential rotation is considered and, following Endal & Sofia (1976,1978), the evolution of angular momentum (J) through the star is followed via a nonlinear diffusion equation (except at the inner border of the convective envelope, where we apply the same formalism of the chemical transport), by enforcing rigid rotation in convective regions (constant angular velocity); Efficiency of both dynamical (Solberg-Hoiland, dynamical shear) and secular (Eddington-Sweet circulation, Goldreich-Shubert-Fricke, secular shear) instabilities are evaluated by computing the corresponding diffusion coefficients as described in Heger et al. (2000), but without their proposed fμ and fc; Angular momentum transport equation is solved contemporary to the chemical evolution equations to take into account the feedback of chemical mixing on molecular weight profile, which could inhibit secular instabilities (μ-current); In solving the angular momentum transport and chemical mixing equations, we computed the effective diffusion coefficient as the sum of the convective one and those related to secular and dynamical rotationally instabilities; No magnetic braking is considered. PRELIMINARY

31. THANKS!