AGB碳化硅星尘中的反应速率不确定性和~（26）Al
Reaction rate uncertainties and 26Al in AGB silicon carbide stardust
摘要：
星尘是一种前太阳颗粒，每一种都是理想的未受污染的恒星样本。主流碳化硅（SiC）星尘形成于富碳渐近巨星分支（AGB）恒星的扩展包层中，并包含放射性核26 Al作为微量元素。本文的目的是详细分析核不确定性的影响，特别是高达四个数量级的大不确定性有关的26 Al_g+（p，γ）27 Si反应速率，在AGB星的生产26铝和比较模型预测的SiC星尘颗粒的实验室分析获得的数据。还简要讨论了恒星的不确定性。我们使用一个详细的核合成后处理程序来计算不同质量（M = 1.75，3和5 Msun）和金属丰度（Z = 0.02，0.012和0.008）的AGB星表面的26 Al/27 Al比值。对于26 Al_g（p，gamma）27 Si反应速率的下限和推荐值，预测的26 Al/27 Al比复制了在SiC晶粒中测量的26 Al/27 Al比范围的上限值。相反，对于26 Al_g（p，γ）27 Si反应速率的上限，预测的26 Al/27 Al比低约100倍，并且低于在SiC晶粒中观察到的范围。当考虑不同的质量和金属丰度的模型时，在恒星SiC晶粒中测量的26 Al/27 Al比率的一个数量级以上的扩展是不可复制的。我们提出了两种方案来解释在主流SiC中观察到的26 Al/27 Al比率的扩散，这取决于26 Al_g +p反应速率的选择。一个涉及不同的星尘形成时间，另一个涉及额外的混合过程。在未来的核实验中获得更多关于26Al_g+p反应的信息后，将有可能得出更有力的结论。
英文摘要：
Stardust is a class of presolar grains each of which presents an ideally uncontaminated stellar sample. Mainstream silicon carbide (SiC) stardust formed in the extended envelopes of carbon-rich asymptotic giant branch (AGB) stars and incorporated the radioactive nucleus 26Al as a trace element. The aim of this paper is to analyse in detail the effect of nuclear uncertainties, in particular the large uncertainties of up to four orders of magnitude related to the 26Al_g+(p,gamma)27Si reaction rate, on the production of 26Al in AGB stars and compare model predictions to data obtained from laboratory analysis of SiC stardust grains. Stellar uncertainties are also briefly discussed. We use a detailed nucleosynthesis postprocessing code to calculate the 26Al/27Al ratios at the surface of AGB stars of different masses (M = 1.75, 3, and 5 M_sun) and metallicities (Z = 0.02, 0.012, and 0.008). For the lower limit and recommended value of the 26Al_g(p,gamma)27Si reaction rate, the predicted 26Al/27Al ratios replicate the upper values of the range of the 26Al/27Al ratios measured in SiC grains. For the upper limit of the 26Al_g(p,gamma)27Si reaction rate, instead, the predicted 26Al/27Al ratios are approximately 100 times lower and lie below the range observed in SiC grains. When considering models of different masses and metallicities, the spread of more than an order of magnitude in the 26Al/27Al ratios measured in stellar SiC grains is not reproduced. We propose two scenarios to explain the spread of the 26Al/27Al ratios observed in mainstream SiC, depending on the choice of the 26Al_g+p reaction rate. One involves different times of stardust formation, the other involves extra-mixing processes. Stronger conclusions will be possible after more information is available from future nuclear experiments on the 26Al_g+p reaction.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
