AAS 199th meeting, Washington, DC, January 2002
Session 143. Stellar Spectroscopy
Oral, Thursday, January 10, 2002, 10:00-11:30am, Jefferson West

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[143.03] s-Process in Shell Carbon Burning

L.-S. The, B.S. Meyer (Clemson University), M.F. El Eid (American University of Beirut)

We present a study of carbon-shell s-process nucleosynthesis in a 25 M\odot model having solar-like initial composition as a follow-up of our previous s-process study of core helium burning. The source of free neutrons, as in the core helium burning, is the 22Ne(\alpha,n)25Mg reaction with the initial 22Ne is what left from the core helium burning. We show the temperature, density, neutron density, and 12C, 22Ne, 80Kr, 86Sr, 87Rb mass fractions evolution during the carbon-shell burning. The model produces a neutron exposure of ~1 mbarn-1 and a peak neutron density of ~1\times1011 cm-3 at the inner edge of carbon shell (mass radius ~2 M\odot) with the duration of s-process of ~1 year. We find all isotopes except 64Zn with proton number between 30 and 40 have an overproduction factor larger than unity in the carbon-shell s-process. These overlay the core helium overproduction factors. The isotopes that are strongly produced are 180Ta, 23Na, 70,72,73,74Ge, 80,82,83Kr, 69,71Ga, 76,77,78,80Se, 66,67,68Zn, 64Ni, 75,79Br, 87Rb, 79,81Br. The isotopes that are strongly destroyed during carbon-shell burning are 58Fe, 64Zn, 63,65Cu, 152Gd, 158Dy, 37Cl, 113In.

This work is supported by NSF grant AST-9819877.

The author(s) of this abstract have provided an email address for comments about the abstract: tlihsin@hubcap.clemson.edu

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