The s-process in massive stars is analyzed as a function of metallicity. The nucleosynthesis occurring in both core helium and shell carbon burning is investigated by numerically modeling nuclear reaction networks, subject to the conditions provided by stellar models. The s-process in massive stars is found to be 'secondary-like' in the disk, the amount of s-process matter ejected being roughly proportional to Fe. In the halo, the s-efficiency drops at low metallicities, with Fe/H below about -2. The elemental s-contributions from massive stars to the solar abundances from iron to zirconium are presented. It is concluded that the weak component can account for a consistent fraction of the solar Cu, Ga, Ge, and Se. The evolutionary trends of elements such as Co, Ni, Cu, Zn, Rb, Sr, Y, and Zr are discussed in comparison with observations of stars belonging to the halo, where massive stars give their major imprint.
S-processing in massive stars as a function of metallicity and interpretation of observational trends
BUSSO, Maurizio Maria;
1992
Abstract
The s-process in massive stars is analyzed as a function of metallicity. The nucleosynthesis occurring in both core helium and shell carbon burning is investigated by numerically modeling nuclear reaction networks, subject to the conditions provided by stellar models. The s-process in massive stars is found to be 'secondary-like' in the disk, the amount of s-process matter ejected being roughly proportional to Fe. In the halo, the s-efficiency drops at low metallicities, with Fe/H below about -2. The elemental s-contributions from massive stars to the solar abundances from iron to zirconium are presented. It is concluded that the weak component can account for a consistent fraction of the solar Cu, Ga, Ge, and Se. The evolutionary trends of elements such as Co, Ni, Cu, Zn, Rb, Sr, Y, and Zr are discussed in comparison with observations of stars belonging to the halo, where massive stars give their major imprint.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
