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首页> 外文期刊>The Astrophysical journal >THE DYNAMICAL EVOLUTION OF THE CIRCUMSTELLAR GAS AROUND LOW- AND INTERMEDIATE-MASS STARS. Ⅰ. THE ASYMPTOTIC GIANT BRANCH
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THE DYNAMICAL EVOLUTION OF THE CIRCUMSTELLAR GAS AROUND LOW- AND INTERMEDIATE-MASS STARS. Ⅰ. THE ASYMPTOTIC GIANT BRANCH

机译：低质量和中等质量恒星周围的环状气体的动力学演化。 Ⅰ。渐近的巨型分支

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We have investigated the dynamical interaction of low- and intermediate-mass stars (from 1 to 5 solar mass) with their interstellar medium (ISM). In this first paper, we examine the structures generated by the stellar winds during the asymptotic giant branch (AGB) phase using a numerical code and the wind history predicted by stellar evolution. The influence of the external ISM is also taken into account. We find that the wind variations associated with the thermal pulses lead to the formation of transient shells with an average lifetime of ～20,000 yr and, consequently, do not remain recorded in the density or velocity structure of the gas. The formation of shells that survive at the end of the AGB phase occurs via two main processes: shocks between the shells formed by two consecutive enhancements of the mass loss or continuous accumulation of the material ejected by the star in the interaction region with the ISM. Our models show that the mass of the circumstellar envelope increases appreciably because of the ISM material swept up by the wind (up to ～70% for the 1 solar mass stellar model). We also point out the importance of the ISM on the deceleration and compression of the external shells. According to our simulations, large regions (up to 2.5 pc) of neutral gas surrounding the molecular envelopes of AGB stars are expected. These large regions of gas are formed from the mass loss experienced by the star during the AGB evolution.
机译：我们研究了低质量和中等质量恒星（从1到5个太阳质量）与其星际介质（ISM）的动力学相互作用。在第一篇论文中，我们使用数字代码和通过恒星演化预测的风向历史检查了在渐近巨型分支（AGB）阶段恒星风产生的结构。还考虑了外部ISM的影响。我们发现，与热脉冲相关的风的变化导致形成了平均寿命约为20,000年的瞬态壳，因此，没有在气体的密度或速度结构中保留记录。在AGB阶段结束时幸存的壳的形成是通过两个主要过程发生的：壳之间的震动是由质量损失的两个连续增强形成的，或者是恒星在与ISM相互作用区域中连续释放的恒星所喷射出的物质。我们的模型显示，由于ISM物质被风吹走，因此星际包膜的质量明显增加（对于1个太阳质量恒星模型，其高达〜70％）。我们还指出了ISM对外壳减速和压缩的重要性。根据我们的模拟，预计在AGB星的分子包膜周围会存在大范围（最多2.5 pc）的中性气体。这些大面积的气体是由恒星在AGB演化过程中经历的质量损失形成的。

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