内禀和外赋AGB星的重核素丰度分析

The Heavy-nuclide Abundances of the Intrinsic and Extrinsic Asymptotic Giant Branch Stars

以１３Ｃ（α，ｎ）１６Ｏ及２２Ｎｅ（α，ｎ）２５Ｍｇ作为双脉冲中子源，对于低质量ＡＧＢ星，采用无分叉ｓ－过程反应通道，结合最近恒星演化的计算结果，在各物理参量合理取值范围内，计算了ＡＧＢ星Ｈｅ壳层内，表面重核素的丰度，在此基础上将星风吸积模型同内禀ＡＧＢ星核合成模型结合起来计算外赋ＡＧＢ星重元素的超丰。

おn this paper we present the nucleosynthesis calculations for the AGB stars during the He-shell flash phase.The main neutron source at the origin of s-process nucleosynthesis is assumed to be the reaction13C(α,n)16O; a minor contribution derives also from the marginal activation of the reaction22Ne(α, n)25Mg at the end of each flash.We adopt a unbranched s-process network,and use standard models for the recurrent thermal pulses:core mass increasing with pulse number,overlap factor and stellar winds varying with core mass. After asymptotic abundances have been achieved,the distributions of s-nuclei can be simply characterized by τ0.The distributions of heavy-nuclide abundances in the He-shell and envelope of the AGB star are given.Taking account of δr≠0,through the equation of conservation of orbital angualar momentum,orbital parameter equations on the mass change are re-deduced.Combined with wind accretion equations,calculations of nucleosynthesis for intrnsic AGB stars first used to calculate s-elements enrichment of the extrinsic AGB stars.The distributions of heavy-nuclide abundances in the envelope of the extrinsic AGB star are also given.