1 / 18

Why Galaxies care about Asymptotic Giant Branch stars

Why Galaxies care about Asymptotic Giant Branch stars. S. Cristallo (INAF - Osservatorio Astronomico di Teramo). Collaborators : O. Straniero, R. Gallino, L. Piersanti, I. Dominguez, M.T. Lederer. OUTLINE. The importance of AGB stars

ethan-ballard
Download Presentation

Why Galaxies care about Asymptotic Giant Branch stars

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Why Galaxies care about Asymptotic Giant Branch stars S. Cristallo (INAF - Osservatorio Astronomico di Teramo) Collaborators: O. Straniero, R. Gallino,L. Piersanti, I. Dominguez, M.T. Lederer

  2. OUTLINE • The importance of AGB stars • Major improvements on the stellar code (FRANEC) • AGB nucleosynthesis and evolution at different metallicities • Very low metallicityAGBs : chemical features

  3. Why AGBs are so important… • Excellent tracings of halo structures; • IR emission (effects on integrated colors); • tracers of intermediate age populations (IZw18); • distance indicators (Mira); • production sites of LIGHT & HEAVY elements.

  4. CORE Earth-Sun (~200 RSUN) AGB structure (1) MAIN REFERENCES: Chieffi et al. (1998) Straniero et al. (2005) Cristallo (2006), PhD Thesis(*) Cristallo et al. (2007) (*) available at http://www.oa-teramo.inaf.it/osservatorio/personale/cristallo/pag_in_eng.html

  5. 13C(α,n)16O 22Ne(α,n)25Mg AGBstructure (2)

  6. The resulting 13C pockets X(13Ceff)=X(13C)-X(14N)*13/14 1st ΔM~10-3M 11th 14N strong neutron poison via 14N(n,p)14C reaction

  7. THE NETWORK About 500 isotopes linked by more than 700 reactions LEGENDA: Light elements Heavy elements

  8. Radiative burning of 13C(α,n)16Oreaction FRANEC C/O~50 C/O~8 M=2M Z=1.0x10-4 M=2M C/O~2 Z=Z (Z=1.4x10-2) C/O>1 FRANEC

  9. Molecular opacities O-rich regime C-rich regime CO H2O TiO CN C2 C3 … … Grains Molecular opacities Atomic opacities T 2000 K 4000-5000 K (*) Cristallo et al. in preparation (+) Cristallo et al. 2007 (ApJ 667, 489)

  10. The models

  11. The s-process: RESUME Z=1.4x10-2 Z= 3.0x10-3 Z=1.0x10-4 Final distributions

  12. YIELDS

  13. AGB evolution at very low metallicities M=2MSUN Z=10-4 M=1.5MSUN Z=5x10-5 Cristallo et al. 2007 (ApJ 667, 489)

  14. The proton ingestion mechanism • Low time steps Time dependent mixing • Rapid structure reaction Coupling between phisical and chemical evolution • Large neutron densities (nn~1015 cm-3) 700 isotopes & 1000 reactions Work in progress!! Z= 5.0 x 10-5 M= 0.85 M M= 1.0 M M= 1.5 M M= 2.0 M M= 2.5 M Hollowell et al. (1990) Iwamoto et al. (2004) Suda et al. (2004) Straniero et al. (2005) Campbell et al. (2007)

  15. Effects of the Huge Pulse 12C/13C Nitrogen

  16. Litium Heavy elements

  17. The importance of using a FULL nuclear network FULL REDUCED

  18. THE STATE OF THE ART • First AGB models calculated with C-enhanced low temperature opacity coefficients, with the formation of a non-negligible 13C-pocket and calculated with a complete nuclear network; • AGB models at very low metallicity: an alternative scenario to the 13C-pocket spread requested by observations?

More Related