The Galactic WC stars Stellar parameters from spectral analyses indicate a new evolutionary sequence
The Galactic WC stars Stellar parameters from spectral analyses indicate a new evolutionary sequence
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银河系 WC 恒星光谱分析的恒星参数表明了新的演化序列
DOI：
10.1051/0004-6361/201117830
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
H. Todt
中科院分区：
文献类型：
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作者：
A. Sander;W.-R. Hamann;H. Todt
大质量恒星从主序星到超新星爆发或伽马射线爆发的生命周期尚不完全清楚，光谱分析的经验结果与当前的演化模型部分冲突。沃尔夫-拉叶星的光谱分析需要详细的非LTE膨胀恒星大气的建模。银河系WN星已经全面分析了这种模型的最新阶段的复杂性，而同样全面的研究银河系WC样本仍然undefined.AimsWe的目标是建立恒星参数和质量损失率的银河系WC星。这些数据提供的经验基础的研究（一）WC星的作用，在大质量的恒星的演化，（二）风驱动机制，和（三）WC星的反馈作为输入模型的化学和动力学演化的galaxys.MethodsWe分析了几乎完整的样品未被遮挡的银河系WC星，使用光谱以及紫外光谱时可用。观测结果与理论光谱拟合，使用波茨坦沃尔夫-拉叶（PoWR）模式大气代码。已为WC亚型WC 4-WC 8范围建立了大型行空白模型网格，并为WC 9参数域建立了较小的网格。WO星和WN/WC凌日类型也分析了使用特殊models.ResultsStellar和大气参数推导出超过50银河系WC和两个WO星，几乎涵盖了整个银河系WC人口，只要恒星是单一的，和unobscured在视觉上。在赫罗图中，WC星位于氢和氦零龄主序星之间，光度L为104.9 - 105.6L <$。质量损失率与L0.8的比例非常紧密。在我们的样本中的两个WO星原来是突出的热（约200 kK），并不适合WC scheme.ConclusionsBy比较经验WC的位置在Hertzsprung-Russell图与进化模型，从最近的超新星统计，我们得出结论，WC星已经从初始质量之间的20太阳质量和45 M的演化。与先前的假设相反，WC星似乎一般不是从最大质量的恒星演化而来。只有WO星可能起源于最初质量超过45 M <$m的祖先星。
ContextThe life cycles of massive stars from the main sequence to their explosion as supernovae or gamma ray bursts are not yet fully clear, and the empirical results from spectral analyses are partly in conflict with current evolutionary models. The spectral analysis of Wolf-Rayet stars requires the detailed modeling of expanding stellar atmospheres in non-LTE. The Galactic WN stars have been comprehensively analyzed with such models of the latest stage of sophistication, while a similarly comprehensive study of the Galactic WC sample remains undone.AimsWe aim to establish the stellar parameters and mass-loss rates of the Galactic WC stars. These data provide the empirical basis of studies of (i) the role of WC stars in the evolution of massive stars, (ii) the wind-driving mechanisms, and (iii) the feedback of WC stars as input to models of the chemical and dynamical evolution of galaxies.MethodsWe analyze the nearly complete sample of un-obscured Galactic WC stars, using optical spectra as well as ultraviolet spectra when available. The observations are fitted with theoretical spectra, using the Potsdam Wolf-Rayet (PoWR) model atmosphere code. A large grid of line-blanked models has been established for the range of WC subtypes WC4 – WC8, and smaller grids for the WC9 parameter domain. Both WO stars and WN/WC transit types are also analyzed using special models.ResultsStellar and atmospheric parameters are derived for more than 50 Galactic WC and two WO stars, covering almost the whole Galactic WC population as far as the stars are single, and un-obscured in the visual. In the Hertzsprung-Russell diagram, the WC stars reside between the hydrogen and the helium zero-age main sequences, having luminositiesLfrom 104.9to 105.6L⊙. The mass-loss rates scale very tightly withL0.8. The two WO stars in our sample turn out to be outstandingly hot (≈200 kK) and do not fit into the WC scheme.ConclusionsBy comparing the empirical WC positions in the Hertzsprung-Russell diagram with evolutionary models, and from recent supernova statistics, we conclude that WC stars have evolved from initial masses between 20 solar masses and 45M⊙. In contrast to previous assumptions, it seems that WC stars in general do not descend from the most massive stars. Only the WO stars might stem from progenitors that have been initially more massive than 45M⊙.