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Understanding Stellar Hydrodynamics: Carbon and Heavy Element Production in Giant Stars

This study explores the hydrodynamic processes in giant stars, focusing on the helium-shell flash convection that results in the production of elements like carbon, oxygen, fluorine, magnesium, sodium, and heavy elements such as barium. We utilize 2D and 3D hydrodynamic simulations to investigate mixing processes at convective boundaries driven by energy from nuclear burning. Our simulations provide insights into elemental overproduction factors in extremely metal-poor stars, allowing for comparisons with observed abundance patterns and enhancing our understanding of early universe astrophysical processes.

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Understanding Stellar Hydrodynamics: Carbon and Heavy Element Production in Giant Stars

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  1. Hydrodynamics processes in stars:Investigating the physics of the nuclear production site of the elements • He-shell flash convection in giant stars: production of carbon, oxygen, F, Mg, Na, and heavy elements like barium. • 2D hydrodynamics simulation: top and bottom stable layer sandwich convectively unstable layer which is • driven by high energy injection from nuclear burning • Shown here: snapshot of entropy fluctuations (2400x800) • Herwig etal. (2006, ApJ 652, 1057)

  2. Hydrodynamics processes in stars:Investigating the physics of the nuclear production site of the elements • Study mixing processes at and across convective boundaries • 3D 5122x256: view of the volume rendered vertical velocity in top 1200km of He-shell flash convection (blue is up velocity and yellow is down) • Herwig, Woodward and Porter (2006, in prep.)

  3. Global stellar evolution and nuclear production computer simulations: understanding and interpreting observations Top panel:simulated total overproduction factors (log units) of various elements in mass ejected from extremely metal poor giant stars for 5 different initial masses Bottom panel:observed overabundance factors (same log units) in observed stars of similar low metal content that have accreted significant amounts of matter from giant stars Herwig (2004, ApJS, 155, 651) Sivarani etal. (2006, ApJ in press, astro-ph/0608112) • Extremely metal poor stars trace astrophysical processes in the early Universe • Our simulations account accurately for several observed properties, e.g. good agreement between 4Msun simulation (top panel) and observed star CS 29528-041. • Other features are not understood, e.g. Na in CS 31080-095 or CNO ratios in CS 22958-042. For these cases we study physical processes in more detail with hydrodynamic models (see previous slide) and incorporate the results into the global simulations shown here.

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