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Low- and intermediate mass stellar evolution and recurrent H-ingestion events in super-AGB thermal pulses s r a t s B Marco Pignatari (Basel) G A - r e p Bill Paxton (KITP) u s n i n Paul Woodward (U Minnesota) o i t s u

  1. Low- and intermediate mass stellar evolution and recurrent H-ingestion events in super-AGB thermal pulses s r a t s B Marco Pignatari (Basel) G A - r e p Bill Paxton (KITP) u s n i n Paul Woodward (U Minnesota) o i t s u Sam Jones, Michael Bennett (Keele) b m o c - Falk Herwig H Dept. of Physics and Astronomy University of Victoria Wednesday, 12 October, 11

  2. Fornax Sculptor Sagittarius Carina MW Nuclear astrophysics and 2.0 a near-field cosmology 1.0 [Ba/Fe] 0 s –1.0 • understanding SFH and chemical r 1.5 a evolution in dSph galaxies b t s 1.0 • constrain nucleosynthesis processes, B [Eu/Fe] 0.5 e.g. Eu vs α -elements G • near-field cosmology: identify the 0 A building blocks of our galaxy –0.5 - r –2 –1 0 e [Fe/H] p Figure 13 Fornax Sculptor Sagittarius Carina MW u Redshift 1.0 5 3 2 1 0.5 s a 1.2 Carina –2 a b 0.5 n i 1.0 [Mg/Fe] 0 n SFR (10 –3 M ☉ year –1 kpc –2 ) 0 o 0.8 –0.5 i t M R s 0.6 u 1.0 2 b b 0.2 0.5 m [Ca/Fe] 4 0 o 0 c –0.5 0 0.5 1.0 1.5 1.0 5 - Now –0.5 ( B – R ) 0 t (Gyear) H Figure 4 –2 –1 0 ( a ) A color-magnitude diagram of the Carina dwarf spheroidal (obtained by M. Mateo with the CTIO 4-m [Fe/H] and MOSAIC camera, private communication) in the central 30 � of the galaxy. This clearly shows the presence of at least three distinct MSTOs. ( b ) The star-formation history of the central region of Carina Figure 11 determined by Hurley-Keller, Mateo & Nemec (1998), showing the relative strength of the different bursts. The ages are also shown in terms of redshift. Tolstoy etal 2009 (ARAA) 2 Wednesday, 12 October, 11

  3. The hierarchy of GCE simulation types s • analytic models, incl. one or a few zones, r a parameterized everything (e.g. Matteucci, t s Timmes, Travaglio, and many more) B • semi-analytical models, amounts to a post- G processing along a cosmological merger- A - tree from simulations (e.g. Font etal., r e Tumlinson and collaborators, and many p more) u s • cosmological simulations with multiple Fabio Governato, U Washington, Seattle n tracer fields (e.g. Kobayashi, Zolotov etal. i n 2010) o i t s u “observed” halo stars in a b m cosmological high-resolution o disc galaxy simulation, c separating out in-situ stars (red - H triangles) and accreted stars ( black dots ) 3 Wednesday, 12 October, 11

  4. For all these applications an internally consistent simulation data set of yields is needed ....... s Available AGB and SNII Yields r a t rP rP sP s B G A solar - Metallicity r e p 1/5 th solar u s n i n primordial o i t s M/M ! u b m Implemented o c - H Carolyn Peruta Michigan State University 4 Wednesday, 12 October, 11

  5. overall s-process indices in AGB stars s r a NuGrid: Set 1 t s hs: <Ba, La, Ce, Nd, La, Sm> B G ls: <Y, Zr> A - r e p u s n i n o i t s u b m o c - H observations and parameterized models (Busso etal 2001) 5 Wednesday, 12 October, 11

  6. 22 Ne( α ,n) reaction rate uncertainty impact s r a t s B G A - r e p u s n i n o i t s u b m o c - H 6 Wednesday, 12 October, 11

  7. Branching at 95 Zr in AGB stars s r a t s B Figure 7 Detail of the chart of isotopes from zirconium to molybdenum. Unstable isotopes G are represented in yellow. The thicker red line shows the main path of the s process; the A thinner red line shows generally less important side branches. The additional numbers in the boxes give the half-life of unstable isotopes and the isotopic abundance fraction for the stable - r isotopes. e p u s n i n o i t s u b m o c - H Lugaro etal 2003 7 Wednesday, 12 October, 11

  8. OVerview low- and intermediate mass stars I s r a t s B G A - r e p u s n i n o i t s u b m o c - H Herwig 2005, ARAA 8 Wednesday, 12 October, 11

  9. OVerview low- and intermediate mass stars II s r a t s B G A - r e p u s n i n o i t s u b m o c - H 9 Wednesday, 12 October, 11

  10. Multi-dimensional stars He-shell flash convection s 2D and 3D plane-parallel r a box-in-a-star (Herwig etal t s 2006) B G A - 2D entropy r e fluctuations p (2400x800), realistic u heating rate s Courant time scale n at this resolution: i ~3*10 -3 sec -> 1.6M n o cycles i t s u b m o c quantify “overshooting” - develop - f top ~ 0.10 H models for 1D stellar evolution f bot,1 ~ 0.01 Herwig etal, 2008 f bot,2 ~ 0.14 Freytag & Herwig, in prep 10 Wednesday, 12 October, 11

  11. Entrainment He-shell flash convection s r a t s B G A - r e p u s n i n o i t s u b 4 π 3D simulations: m concentration of fluid o c “above” (with Woodward, - H LCSE Minnesota) 11 Wednesday, 12 October, 11

  12. Building sub-grid models for 1D stellar evolution s r a t s diffusion coefficient analysis B (with Michael Bennett@Keele) G A - r e p u s n i n o i t s u b m o c - H 12 Wednesday, 12 October, 11

  13. The H-ingestion (core/shell) flash in low-metallicity RGB/AGB stars s r a t s B G A - r e p u s n i n o i t For [Fe/H] <-2.5 (Suda etal. 2004) s u 5M sun , Z=0.0, 10th TP , Herwig 2002 b Iwamoto etal (2004): the site for s-process in m EMP AGB stars o see also more recent work by: c 12 C(p, γ ) 13 N( β + ) 13 C( α ,n) 16 O Campbell etal - H Cristallo etal Lau etal and others 13 Wednesday, 12 October, 11

  14. More examples Numerous instances of convective-reactive phases in the literature, in the context of Pop III: Fujimoto etal. (1990), Hollowell etal. (1990), Iwamoto etal (2004), Fujimoto etal s r (2000), Herwig (2003), Chieffi etal (2001), Weiss etal. (2004), Schlattl etal (2001), a t Picardie etal (2004), Suda etal (2004) … s B 2Msun, Z=0 G A - r e p u s n i n o i t s u b m o c - H … also in massive Pop III and II.5 and X-ray Iwamoto etal. 2004 bursts. 14 Wednesday, 12 October, 11

  15. Convective-reactive event in 1M s Pop III stellar models (with MESA code, Bill Paxton) s r a t s B G A - r e p u s n i n o 4 i t s log Luminosity L � 2 u b m 0 o c − 2 - H − 4 5 . 0 4 . 5 4 . 0 3 . 5 log Te ff 15 Wednesday, 12 October, 11

  16. Other examples at near-solar metal content: s r a • X-ray bursts (Woosely etal 2004, Piro & Bildsten 2007) t s B • accreting white dwarfs, SNIa progenitors (Cassisi etal 1998) G A • post-RGB late He-flashers (Brown etal 2001, Miller - r e p Bertolami etal 2008) u s • post-AGB He-flashers (Schönberner 1979; Iben 1983, 1995; n i n o Herwig etal 1999, 2001; Miller-Bertolami etal 2006) i t s u b m o c - H 16 Wednesday, 12 October, 11

  17. H-combustion in stellar evolution convective mixing of H into 12 C-rich He-convection zone T ~ 150-300MK, t mix ~1000 s r a t The ratio of the mixing time scale and the reaction time scale is called the Damköhler number: s B D α = τ mix G . τ react A - r Dimotakis, P. E. 2005, Annu. Rev. Fluid Mech., 37, 329 e p u s • D α <<1: fully mixed burning, MLT appropriate n i • D α ~1 : combustion regime, MLT and 1D spherical n o symmetry assumption inappropriate because: i t ★ MLT describes convection only in a time and s u spatially averaged sense b ★ in combustion fuels are not completely m mixed o c ★ fluid elements have a range of velocity - - H broadens the burning front ★ localized energy feedback from nuclear burn feeds back into hydro 17 Wednesday, 12 October, 11

  18. H-combustion provides naturally a neutron source under “non-standard” conditions 12 C(p, γ ) 13 N( β + ) 13 C( α ,n) 16 O s r a t s B G A - r e p u s n i n o i t s u b m o c - H 18 Wednesday, 12 October, 11

  19. How can we better understand these s H-combustion events? r a t s B Need cases with many observables that can test G A simulations of convective-reactive combustion! - r e p u s Post-AGB flashers are such validation cases! n i Sakurai’s object. n o i t s u b m o c - H 19 Wednesday, 12 October, 11

  20. Combustion in the post-AGB flasher s r a t s B G A - r e p u s n i n o i t s u b m o c - H 20 Wednesday, 12 October, 11

  21. Post-AGB/young white dwarf He-shell flash object Sakurai’s object s r a t s B G A - r e p u s n i n o i Hajduk, Zijlstra, Herwig etal., t s u Science 308, 231, 2005. b m o c - van Hoof etal 2007, 2005/06: radio H observation with VLA 21 Wednesday, 12 October, 11

  22. Highly non-solar, H-deficient abundance distribution of Sakurai’s Object in 1996 s r a t s B G A - r e p u s n i n o i t s u b m o c - H Asplund etal 1999 22 Wednesday, 12 October, 11

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