Driving classical Wolf-Rayet winds: A Γ- and Z-dependent mass-loss
Driving classical Wolf-Rayet winds: A Γ- and Z-dependent mass-loss
复制标题
驱动经典沃尔夫拉叶风：A 和 Z 相关的质量损失
DOI：
10.1093/mnras/stz3064
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发表时间：
2019
影响因子：
4.8
通讯作者：
Hamann
中科院分区：
文献类型：
--
作者：
Sander;A. A. C;Hamann
经典的Wolf-Rayet(CWR)恒星正处于制约大质量恒星命运的关键进化阶段。这些热的、耗氢的恒星的反馈通过注入巨大的电离辐射和动能来控制它们周围的环境。Wolf-Rayet(WR)风的强度决定了其残留物的最终质量，可能是一个巨大的黑洞。然而，尽管它们对引力波探测统计数据有重大影响和重要性，但对WR风的了解尤其有限。在这篇文章中，我们介绍了第一套流体力学一致的恒星大气模型，用于描述碳(C)和氮(N)序列的CWR星，即WC星和WN星，它们是恒星光度质量比(或Eddington Gamma)和金属丰度的函数。我们证明了CAK风理论对CWR恒星的不适用性，并证实了早先的发现，即它们的风是在(热的)铁(Fe)不透明度峰值发射的。对于LogZ/Z⊙>；−2，Fe也是贯穿整个风的主要加速器。与之前声称的WR恒星质量损失下限大幅降低相比，我们获得了平稳过渡到光学稀薄风的结论。此外，我们发现，在太阳和亚太阳金属丰度下，质量损失率都强烈依赖于爱丁顿Γ。结果表明，WC碳和氧丰度的增加略微降低了预测的质量损失率。太阳以下金属含量的计算表明，在小麦哲伦星云的金属含量以下，WR质量损失率的下降速度比之前假设的要快得多，这可能允许即使在局部宇宙中也有较高的黑洞质量。
Classical Wolf–Rayet (cWR) stars are at a crucial evolutionary stage for constraining the fates of massive stars. The feedback of these hot, hydrogen-depleted stars dominates their surrounding by tremendous injections of ionizing radiation and kinetic energy. The strength of a Wolf–Rayet (WR) wind decides the eventual mass of its remnant, likely a massive black hole. However, despite their major influence and importance for gravitational wave detection statistics, WR winds are particularly poorly understood. In this paper, we introduce the first set of hydrodynamically consistent stellar atmosphere models for cWR stars of both the carbon (C) and the nitrogen (N) sequence, i.e. WC and WN stars, as a function of stellar luminosity-to-mass ratio (or Eddington Gamma) and metallicity. We demonstrate the inapplicability of the CAK wind theory for cWR stars and confirm earlier findings that their winds are launched at the (hot) iron (Fe) opacity peak. For logZ/Z⊙> −2, Fe is also the main accelerator throughout the wind. Contrasting previous claims of a sharp lower mass-loss limit for WR stars, we obtain a smooth transition to optically thin winds. Furthermore, we find a strong dependence of the mass-loss rates on Eddington Γ, both at solar and subsolar metallicity. Increases in WC carbon and oxygen abundances turn out to slightly reduce the predicted mass-loss rates. Calculations at subsolar metallicities indicate that below the metallicity of the Small Magellanic Cloud, WR mass-loss rates decrease much faster than previously assumed, potentially allowing for high black hole masses even in the local Universe.