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The s-Process in AGB Stars

Published online by Cambridge University Press:  30 March 2016

R. Gallino ,
C.M. Raiteri  and
M. Busso
R. Gallino
Affiliation:
Istituto di Fisica Generale dell’Universita‘, Via P. Giuria 1, 10125 Torino, Italy
C.M. Raiteri
Affiliation:
Osservatorio Astronomico di Torino, Strada Osservatorio SO, 10025 Pino Torinese, Italy

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The evidence of an exponential distribution of neutron exposures for reproducing the solar-system s-isotopes between Zr and Pb, the main component, comes from a phenomenological analysis of the s-path in the σN versus A plot (see Käppeler, Beer and Wisshak, 1989). The resulting mean neutron exposure is τ0 = 0.30 ± 0.01 mb−1. The study of branchings with no or weak temperature dependence (95Zr; 147Nd, 147,148Pm; 185W, 186Re) allows one to derive an effective neutron density nn =(3.4±1.0)×108cm−3. On the other hand, an effective temperature is obtained from the branchings 134’135Cs, 151Sm, 154Eu and 176Lu: T8 = 3.4 ± 0.5 (Käppeler et al., 1990). Although the phenomenological approach is very useful because it is independent of stellar models, nonetheless it can only lead to effective physical conditions, symplifying the complexity of the astrophysical sites.

Type
Joint Commission Meetings
Information
Highlights of Astronomy , Volume 9: Highlights of Astronomy. As presented at the XXIst General Assembly of the IAU, 1991 , 1992 , pp. 623 - 625
Copyright
Copyright © Kluwer 1992

References

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