Background: Most of the stars in the Universe will end their evolution by losing their envelope during the thermally pulsing asymptotic giant branch (TP-AGB) phase, enriching the interstellar medium of galaxies with heavy elements, partially condensed into dust grains formed in their extended circumstellar envelopes. Among these stars, carbon-rich TP-AGB stars (C-stars) are particularly relevant for the chemical enrichment of galaxies. We here investigated the role of the metallicity in the dust formation process from a theoretical viewpoint. Methods: We coupled an up-to-date description of dust growth and dust-driven wind, which included the time-averaged effect of shocks, with FRUITY stellar evolutionary tracks. We compared our predictions with observations of C-stars in our Galaxy, in the Magellanic Clouds (LMC and SMC) and in the Galactic Halo, characterised by metallicity between solar and 1/10 of solar. Results: Our models explained the variation of the gas and dust content around C-stars derived from the IRS Spitzer spectra. The wind speed of the C-stars at varying metallicity was well reproduced by our description. We predicted the wind speed at metallicity down to 1/10 of solar in a wide range of mass-loss rates.

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富含碳的恒星周围的尘埃产生：金属性的作用

背景：宇宙中的大多数恒星将通过在热脉冲渐近巨星分支 (TP-AGB) 阶段失去它们的包层来结束它们的演化，从而使星系的星际介质富含重元素，部分凝聚成在它们的扩展中形成的尘埃颗粒。星周信封。在这些恒星中，富含碳的 TP-AGB 星（C 星）与星系的化学富集特别相关。我们在这里从理论的角度研究了金属含量在粉尘形成过程中的作用。方法：我们将尘埃生长和尘埃驱动风的最新描述与 FRUITY 恒星演化轨迹相结合，其中包括冲击的时间平均效应。我们将我们的预测与对银河系、麦哲伦星云（LMC 和 SMC）和银河晕中 C 星的观测进行了比较，金属丰度介于太阳光和太阳光的 1/10 之间。结果：我们的模型解释了来自 IRS 斯皮策光谱的 C 星周围气体和尘埃含量的变化。我们的描述很好地再现了 C 星在不同金属丰度下的风速。我们预测了在各种质量损失率下金属丰度下风速低至太阳能的 1/10。