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Presolar grains from meteorites: AGB star matter in the laboratory
Published online by Cambridge University Press: 25 May 2016
Abstract
Primitive meteorites contain dust grains that predate the Solar System, formed in stellar atmospheres and thus represent samples of ancient Stardust. Among the presolar grain types identified so far, corundum (Al2O3) and silicon carbide (SiC) are inferred to originate from AGB stars. Corundum grains carry the signatures of core H burning in their O isotopes and of shell H burning during the AGB phase in the form of extinct 26Al. In presolar SiC, most of which originated from carbon stars, the C and N isotopes and 26Al reflect core and shell H burning and shell He burning. In addition, many elements that carry the isotopic signature of neutron capture have also been measured. Most individual grains show excesses in 29Si and 30Si, but the contribution from neutron capture is only a minor effect and the major effect is due to galactic heterogeneity. Noble gases and the elements Ba, Nd, Sm, and Dy are measured in ”bulk samples”, collections of many grains. Their measured isotopic patterns are well reproduced by models of the s-process in AGB stars. Recently, the isotopic analysis of Sr, Zr and Mo in single SiC grains has been made possible by resonance ionization mass spectrometry. These measurements also point to low-mass AGB stars as the most likely sources. Specifically, large 96Zr depletions in some grains indicate that the 22Ne(α, n) source was not active in the grains' parent stars.
- Type
- Part 1. Basic Facts, Structure, Evolution, Nucleosynthesis
- Information
- Symposium - International Astronomical Union , Volume 191: Asymptotic Giant Branch Stars , 1999 , pp. 59 - 68
- Copyright
- Copyright © Astronomical Society of the Pacific 1999
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