AI 中文总结
本研究耦合时变质量损失与非平衡化学，模拟红超巨星的分子及尘埃形成，揭示加速星风可产生更多尘埃，且团块状星周介质能更好匹配观测通量，明确了相关因素对红超巨星前身星可观测性质的重要作用。
AI 中文摘要
红超巨星（RSG）被公认为是尘埃的重要来源，可丰富星际介质，但调控其星风尘埃成核的物理条件仍知之甚少。本研究探究RSG中分子与尘埃的形成机制，以及增强的质量损失如何在核心坍缩前形成致密、富尘埃的星周介质（CSM）。我们将时变质量损失与非平衡化学耦合，模拟分子与尘埃前体的形成，所用质量损失率范围为10⁻⁶至10⁻² \u00d7 太阳质量每年，涵盖恒定与加速星风两种轮廓。CO、H₂O、SiO、HCN、CS、SO、NH₃、H₂、O₂等分子在CSM中高效形成，质量介于10⁻¹⁵至10⁻² 太阳质量之间；富氧尘埃（即硅酸盐与氧化铝）占尘埃组成的主导地位，总尘埃质量范围为10⁻⁸至3×10⁻³ 太阳质量。加速星风会产生更多尘埃，并使尘埃在更靠近恒星表面的位置形成，所得通量呈现强烈的中红外过量；9.7与18微米的硅酸盐特征根据CSM的光学深度表现为发射或吸收。我们对SN 2023ixf前身星模型的时变质量损失历史模拟显示，CSM尘埃质量会向爆炸前逐渐增加；团块状CSM与观测到的光学及红外通量匹配度显著更高，表明时变质量损失、CSM结构及星风加速对塑造红超巨星前身星的可观测性质具有重要意义。
英文摘要
Red supergiant (RSG) stars are widely recognized as significant sources of dust, enriching the interstellar medium. However, the physical conditions that regulate dust nucleation in their winds remain poorly constrained. We investigate the formation of molecules and dust in RSG and explore how enhanced mass loss can produce a dense, dust-rich circumstellar medium (CSM) before core collapse. We couple time-dependent mass loss with non-equilibrium chemistry to model the formation of molecules and dust precursors using mass loss rates ranging from 10$^{-6}$ to 10$^{-2}$ \Mdot\ and both constant and accelerating wind profiles. Molecules such as CO, H$_2$O, SiO, HCN, CS, SO, NH$_3$, H$_2$, and O$_2$ form efficiently in the CSM, with masses varying between 10$^{-15}$--10$^{-2}$ \Ms. O-rich dust, namely silicates and alumina, dominates the dust composition. The total dust mass ranges between 10$^{-8}$ and 3$\times$10$^{-3}$ \Ms. Accelerated winds produce more dust and allow dust formation closer to the stellar surface. The resulting fluxes exhibit strong mid-infrared excesses. The 9.7 and 18 \mic\ silicate features appear in either emission or absorption depending on the optical depth of the circumstellar medium. The time-dependent mass-loss history of our SN~2023ixf progenitor models results in a gradual increase in CSM dust mass toward explosion. A clumpy CSM provides a substantially better match to the observed optical and infrared fluxes, demonstrating the importance of time-dependent mass loss, CSM structure, and wind acceleration in shaping the observable properties of red supergiant progenitors.
CommentsSubmitted to The Astrophysical Journal
