COMPLEX ORGANIC AND INORGANIC COMPOUNDS IN SHELLS OF LITHIUM-RICH K GIANT STARS
COMPLEX ORGANIC AND INORGANIC COMPOUNDS IN SHELLS OF LITHIUM-RICH K GIANT STARS
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DOI：
10.1088/0004-637x/806/1/86
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发表时间：
2015-04
期刊：
影响因子：
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通讯作者：
R. Reza;N. Drake;I. Oliveira;S. Rengaswamy
中科院分区：
文献类型：
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作者：
R. Reza;N. Drake;I. Oliveira;S. Rengaswamy
在星际介质中发现的碳氢化合物有机材料以芳香族和脂肪族形式的复杂混合物存在。它被认为起源于富含碳的巨星，处于演化的最后阶段，在它们成为行星状星云的过程中，几千年来发生了非常强烈的质量损失。我们在这里表明，相同的有机化合物似乎是在巨星演化的早期阶段形成的，更具体地说，是在第一升巨分支 K 型恒星期间形成的。根据我们的模型，只有当这些恒星突然富含锂，并在短短几千年内形成质量严重损失的星周壳时，才会发生这种情况。平均来说，这种突然的质量损失比正常的贫锂K巨星大一千倍。这个壳随后会分离，特别是当恒星停止锂富集并且发生光球锂快速耗尽时。为了获得额外的碳基材料来形成有机碳氢化合物，并解释这些恒星中复杂无机化合物的存在，我们提出这些强风与这些恒星周围已经存在的剩余小行星/彗星盘的相互作用，因为它们是矮A型恒星。这里提出的相互作用机制成功地解释了无机化合物的存在；然而，它无法产生新的无碳原子来形成有机烃化合物。最后，我们讨论了一些建议和猜测，这些建议和猜测最终可以帮助解决长期以来困扰李富豪的难题。
Hydrocarbon organic material, as found in the interstellar medium, exists in complex mixtures of aromatic and aliphatic forms. It is considered to originate from carbon-enriched giant stars during their final stages of evolution, when very strong mass loss occurs in a few thousand years on their way to becoming planetary nebulae. We show here that the same organic compounds appear to be formed in previous stages of the evolution of giant stars, more specifically, during the first-ascending giant branch K-type stars. According to our model, this happens only when these stars are being abruptly enriched with lithium, together with the formation of a circumstellar shell with a strong mass loss during just a few thousand years. This sudden mass loss is, on average, a thousand times larger than that of normal Li-poor K giant stars. This shell would later be detached, especially when the star stops its Li enrichment and a rapid photospheric Li depletion occurs. In order to gain extra carbon-based material to form the organic hydrocarbons, as well as to explain the presence of complex inorganic compounds in these stars, we propose an interaction of these strong winds with the remaining asteroidal/cometary disks that already existed around these stars since they were dwarf A-type stars. The mechanism of interaction presented here is successful in explaining the presence of inorganic compounds; however, it is unable to produce new carbon-free atoms to form the organic hydrocarbon compounds. Finally, we discuss some suggestions and speculations that can eventually help solve the long-standing puzzle of Li-rich giants.