AGB stars and presolar grains

Journal Article · Fri May 09 04:00:00 EDT 2014 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.4875288· OSTI ID:22280410

Busso, M.; Trippella, O. ^[1]; Maiorca, E. ^[2]; Palmerini, S. ^[3]

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1. INFN and University of Perugia, Perugia (Italy)
2. INAF - Arcetri Astrophysical Observatory, Firenze, Italy and INFN - Section of Perugia, Perugia (Italy)
3. Departamento de Fìsica Teòrica y del Cosmsos, Universidad de Granada, Granada (Spain)

Among presolar materials recovered in meteorites, abundant SiC and Al{sub 2}O{sub 3} grains of AGB origins were found. They showed records of C, N, O, {sup 26}Al and s-element isotopic ratios that proved invaluable in constraining the nucleosynthesis models for AGB stars [1, 2]. In particular, when these ratios are measured in SiC grains, they clearly reveal their prevalent origin in cool AGB circumstellar envelopes and provide information on both the local physics and the conditions at the nucleosynthesis site (the H- and He-burning layers deep inside the structure). Among the properties ascertained for the main part of the SiC data (the so-called mainstream ones), we mention a large range of {sup 14}N/{sup 15}N ratios, extending below the solar value [3], and {sup 12}C/{sup 13}C ratios ≳ 30. Other classes of grains, instead, display low carbon isotopic ratios (≳ 10) and a huge dispersion for N isotopes, with cases of large {sup 15}N excess. In the same grains, isotopes currently feeded by slow neutron captures reveal the characteristic pattern expected from this process at an efficiency slightly lower than necessary to explain the solar main s-process component. Complementary constraints can be found in oxide grains, especially Al{sub 2}O{sub 3} crystals. Here, the oxygen isotopes and the content in {sup 26}Al are of a special importance for clarifying the partial mixing processes that are known to affect evolved low-mass stars. Successes in modeling the data, as well as problems in explaining some of the mentioned isotopic ratios through current nucleosynthesis models are briefly outlined.

• OSTI ID: 22280410
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 1595; ISSN APCPCS; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
79 ASTRONOMY AND ASTROPHYSICS
ALUMINIUM 26
ALUMINIUM OXIDES
ASTROPHYSICS
CAPTURE
CARBON 12
CARBON 13
COSMOLOGY
DWARF STARS
ELEMENT ABUNDANCE
ISOTOPE RATIO
METEORITES
NITROGEN 14
NITROGEN 15
NUCLEOSYNTHESIS
OXYGEN ISOTOPES
S PROCESS
SILICON CARBIDES