The Supernova Channel of Super-AGB Stars
The Supernova Channel of Super-AGB Stars
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DOI：
10.1086/520872
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发表时间：
2007-05
期刊：
影响因子：
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通讯作者：
A. Poelarends;F. Herwig;F. Herwig;Norbert Langer;Alexander Heger;Alexander Heger;Alexander Heger
中科院分区：
文献类型：
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作者：
A. Poelarends;F. Herwig;F. Herwig;Norbert Langer;Alexander Heger;Alexander Heger;Alexander Heger
我们研究了太阳金属丰度恒星在白色矮星形成和核心坍缩过渡区的晚期演化。这包括超渐近巨星分支（super-AGB，SAGB）恒星，它们点燃碳燃烧并形成氧氖（ONe）核心。SAGB星星的核心可能会因为持续的H-和He-壳燃烧而增长到阿布拉塞卡质量，最终成为核心坍缩的超新星。从恒星演化模型中我们发现SAGB演化的初始质量范围是7.5-9.25 M。我们用三种不同的恒星演化代码进行计算，以判断我们的结果的鲁棒性。质量范围明显取决于对流混合和对流过冲的处理。考虑到大量的热脉冲的影响，如预期的SAGB星，我们构建合成SAGB模型，通过恒星演化模拟校准。合成模型使我们能够计算SAGB恒星从热脉冲开始直到核心达到钱德拉塞卡质量或被星风发现的主要性质的演变。因此，我们区分恒星的初始质量范围，产生ONe WD从导致电子捕获SNe。对于我们的基准模型，后者被发现是9.0-9.25 M，这意味着电子捕获的SNe将占局部宇宙中所有SNe的4%左右。由于第三次挖掘效率和AGB质量损失率的不确定性，这一确定中的误差可能导致电子捕获SNe的数量增加一倍，这为它们对所有超新星的贡献提供了一个确定的上限，约为20%。
We study the late evolution of solar metallicity stars in the transition region between white dwarf formation and core collapse. This includes the super-asymptotic giant branch (super-AGB, SAGB) stars, which ignite carbon burning and form an oxygen-neon (ONe) core. SAGB star cores may grow to the Chandrasekhar mass because of continued H- and He-shell burning, ending as core-collapse supernovae. From stellar evolution models we find that the initial mass range for SAGB evolution is 7.5–9.25 M☉. We perform calculations with three different stellar evolution codes to judge the robustness of our results. The mass range significantly depends on the treatment of semiconvective mixing and convective overshooting. To consider the effect of a large number of thermal pulses, as expected in SAGB stars, we construct synthetic SAGB models that are calibrated through stellar evolution simulations. The synthetic model enables us to compute the evolution of the main properties of SAGB stars from the onset of thermal pulses until the core reaches the Chandrasekhar mass or is uncovered by the stellar wind. Thereby, we differentiate the stellar initial mass ranges that produce ONe WDs from that leading to electron-capture SNe. The latter is found to be 9.0–9.25 M☉ for our fiducial model, implying that electron-capture SNe would constitute about 4% of all SNe in the local universe. The error in this determination due to uncertainties in the third dredge-up efficiency and AGB mass-loss rate could lead to about a doubling of the number of electron-capture SNe, which provides a firm upper limit to their contribution to all supernovae of ~20%.