ar X iv : a st ro - p h / 04 05 06 5 v 1 4 M ay 2 00 4 128 Xe and 130 Xe : Testing He - shell burning in AGB stars
نویسندگان
چکیده
The s-process branching at 128 I has been investigated on the basis of new, precise experimental (n, γ) cross sections for the s-only isotopes 128 Xe and 130 Xe. This branching is unique, since it is essentially determined by the temperature-and density-sensitive stellar decay rates of 128 I and only marginally affected by the specific stellar neutron flux. For this reason it represents an important test for He-shell burning in AGB stars. The description of the branching by means of the complex stellar scenario reveals a significant sensitivity to the time scales for convection during He shell flashes, thus providing constraints for this phenomenon. The s-process ratio 128 Xe/ 130 Xe deduced from stellar models allows for a 9±3% p-process contribution to solar 128 Xe, in agreement with the Xe-S component found in meteoritic presolar SiC grains.
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