[Previous] | [Session 143] | [Next]

[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

[Previous] | [Session 143] | [Next]