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arXiv 1002.2458astro-ph.SR
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质量损失AGB星的红外测光和演化。III。MS和S星的质量损失率

Infrared photometry and evolution of mass-losing AGB stars. III. Mass loss rates of MS and S stars

R. Guandalini

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6 pages, 4 figures, accepted for publication on A&A
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摘要：

上下文渐近巨星分支（AGB）阶段标志着低质量和中等质量恒星演化的结束，它们是质量返回到星际介质和星系化学演化的基本贡献者。对AGB星的光度和距离的了解不足，阻碍了对质量损失过程的详细了解。目标。在一系列的论文中，我们试图建立一个标准，允许更定量的测定光度的各种类型的AGB星，使用红外（IR）通量作为基础。还需要更新质量损失率的汇编，因为它对我们研究这些恒星的演化特性至关重要。在本文中，我们集中我们的分析研究的质量损失率的银河系S星的样本。方法.我们重新分析的银河系MS，S，SC星的样本的恒星风的属性与可靠的估计的距离的基础上先前确定的标准。然后，我们将所得的质量损失率与先前获得的样品的C-丰富的AGB星。结果平均而言，S星的星风效率低于相同光度的富碳AGB星。近中红外颜色在我们的分析中似乎是至关重要的。他们表现出良好的相关性，特别是对Mira星的质量损失率。我们认为，恒星风的速率之间的关系和近-中红外颜色和变化的周期提高了对低质量恒星的晚期演化阶段的理解，并可能是恒星风的速率之间的关系和热星等的起源。

英文摘要：

Context. The asymptotic giant branch (AGB) phase marks the end of the evolution for low- and intermediate-mass stars, which are fundamental contributors to the mass return to the interstellar medium and to the chemical evolution of galaxies. The detailed understanding of mass loss processes is hampered by the poor knowledge of the luminosities and distances of AGB stars. Aims. In a series of papers we are trying to establish criteria permitting a more quantitative determination of luminosities for the various types of AGB stars, using the infrared (IR) fluxes as a basis. An updated compilation of the mass loss rates is also required, as it is crucial in our studies of the evolutionary properties of these stars. In this paper we concentrate our analysis on the study of the mass loss rates for a sample of galactic S stars. Methods. We reanalyze the properties of the stellar winds for a sample of galactic MS, S, SC stars with reliable estimates of the distance on the basis of criteria previously determined. We then compare the resulting mass loss rates with those previously obtained for a sample of C-rich AGB stars. Results. Stellar winds in S stars are on average less efficient than those of C-rich AGB stars of the same luminosity. Near-to-mid infrared colors appear to be crucial in our analysis. They show a good correlation with mass loss rates in particular for the Mira stars. We suggest that the relations between the rates of the stellar winds and both the near-to-mid infrared colors and the periods of variability improve the understanding of the late evolutionary stages of low mass stars and could be the origin of the relation between the rates of the stellar winds and the bolometric magnitudes.

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