We present new evolutionary calculations for a 3 solar mass star of Population Ⅰ starting from the zero-age main sequence and followed up to the 25th thermal pulse of the asymptotic giant branch. The third dredge-up is found to occur in a self-consistent way from the 14th pulse on. We show that any amount of ~(13)C possibly synthesized at the H/He interface during the interpulse period is completely burnt through (α, n) reactions before the next pulse develops. As a consequence, s-elements are produced in a radiative environment, at a neutron density of at most a few 10~7 n cm~(-3). They are then engulfed and diluted into the next convective pulse, where a second (minor) neutron burst occurs, driven by the ~(22)Ne(α, n)~(25)Mg reaction marginally activated near the end of the He-shell instability. Despite the differences of the present model with respect to past calculations, we predict s-process distributions very close to those computed by allowing ~(13)C to burn in convective pulses: ~(13)C burning and the ensuing s-processing are confirmed to account for the main observational and experimental constraints. The reasons for this are briefly discussed. Since no ~(13)C survives the interpulse phase, we conclude that no modifications of the pulse shape due to the energy feedback from the ~(13)C(α, n)~(16)O reaction occur.
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机译：从零年龄主序开始，一直到渐近巨型分支的第25个热脉冲，我们给出了种群Ⅰ的3个太阳质量星的新的演化计算。从第14个脉冲开始，发现第三次挖泥以自洽的方式发生。我们表明，在下一个脉冲产生之前，在脉冲期间在H / He界面上可能合成的任何〜（13）C都通过（α，n）反应完全燃烧掉。结果，在辐射环境中产生s元素，其中子密度至多为10〜7 n cm〜（-3）。然后将它们吞没并稀释到下一个对流脉冲中，在此附近发生第二次（次要）中子爆发，这是由〜（22）Ne（α，n）〜（25）Mg反应在He-附近接近激活而驱动的。外壳不稳定。尽管当前模型与过去的计算存在差异，但我们预测s过程分布非常接近通过允许〜（13）C在对流脉冲中燃烧而计算出的分布：〜（13）C燃烧和随后的s处理是确认占主要的观察和实验约束。简要讨论其原因。由于没有〜（13）C在脉冲间相中幸存，因此我们得出结论，由于〜（13）C（α，n）〜（16）O反应的能量反馈而不会发生脉冲形状的变化。
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