AGB恒星中的尘埃：透明还是不透明？
Dust in AGB stars: transparent or opaque?
摘要：
人们普遍认为，冷巨星在演化后期的风是由尘埃颗粒上的辐射压力驱动的，但实际上负责驱动M型AGB星风的颗粒种类仍然是一个争论的问题（参见Höfner，本卷）。尘埃粒子的光学性质对恒星光谱的影响有两种方式：（i）间接地，通过它们对大气层/包层的动力学结构和由此产生的分子特征的影响;（ii）直接地，通过尘埃颗粒的吸收和散射改变光谱能量分布。C型和M型AGB星在可见光区和近红外区能量分布的质的差异表明，富氧大气中的尘埃粒子对辐射是相对透明的。通过使用详细的动力学模型的气体和辐射结合一个简单的描述的尘埃不透明度（可以调整，以模仿不同的波长依赖性和冷凝温度），也通过调整被视为真正的吸收不透明度的分数，我们调查的尘埃属性产生合成光度与观察一致。这项研究的目的是缩小可能驱动M型AGB恒星风的尘埃种类。
英文摘要：
It is commonly believed that winds of cool giants in their late evolutionary stages are driven by radiative pressure on dust grains, but the actual grain species responsible for driving winds of M-type AGB stars are still a matter of debate (see Höfner, this volume). The optical properties of the dust particles responsible for initiating the outflow affect the stellar spectra in two ways: (i) indirectly, through their influence on the dynamical structure of the atmosphere/envelope and the resulting molecular features, and (ii) directly, by changes of the spectral energy distribution due to absorption and scattering on dust grains. The qualitative differences in the energy distributions of C-type and M-type AGB stars in the visual and near-infrared regions suggest that the dust particles in oxygen rich atmospheres are relatively transparent to radiation. By using detailed dynamical models of gas and radiation combined with a simple description for the dust opacity (which can be adjusted to mimic different wavelength dependencies and condensation temperatures) and also by adjusting the fraction of the opacity that is treated as true absorption, we investigate which dust properties produce synthetic photometry consistent with observations. The goal of this study is to narrow down the possible dust species that may be driving the winds in M-type AGB stars.
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