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arXiv 1209.0455astro-ph.SR
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Zeta Oph和弱风问题

Zeta Oph and the weak-wind problem

V. V. Gvaramadze, N. Langer, J. Mackey

备注：
5 pages, 1 figure, 2 tables. Accepted for publication in MNRAS Letters
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摘要：

质量损失率（$\dot{M}$）是影响大质量恒星演化和观测表现及其对周围介质影响的关键参数之一。尽管它很重要，但晚型O型矮星的经验和理论$\dot{M}$之间存在约100倍的差异，即所谓的弱风问题。在这封信中，我们提出了一个简单的新方法来限制$\dot{M}$失控的大质量恒星通过观察他们的弓激波和Stromgren球，这可能是决定性的重要性，为解决弱风问题。使用这种方法，我们发现著名的逃逸O9.5 V恒星zeta Oph的$\dot{M}$比紫外线（UV）线拟合（Marcolino et al. 2009）得出的高出一个数量级以上，并且比基于Vink et al.（2000）的理论配方和Ha线（Mokiem et al. 2005）的低6至7倍。如果星风是cloudical的，用我们的方法得到的$\dot{M}$与基于紫外线的结果之间的差异将更加严重。同时，我们对$\dot{M}$的估计与Lucy（2010）的移动反转层理论的预测一致。

英文摘要：

Mass-loss rate, $\dot{M}$, is one of the key parameters affecting evolution and observational manifestations of massive stars, and their impact on the ambient medium. Despite its importance, there is a factor of ~100 discrepancy between empirical and theoretical $\dot{M}$ of late-type O dwarfs, the so-called weak-wind problem. In this Letter, we propose a simple novel method to constrain $\dot{M}$ of runaway massive stars through observation of their bow shocks and Stromgren spheres, which might be of decisive importance for resolving the weak-wind problem. Using this method, we found that $\dot{M}$ of the well-known runaway O9.5 V star zeta Oph is more than an order of magnitude higher than that derived from ultraviolet (UV) line-fitting (Marcolino et al. 2009) and is by a factor of 6 to 7 lower than those based on the theoretical recipe by Vink et al. (2000) and the Halpha line (Mokiem et al. 2005). The discrepancy between $\dot{M}$ derived by our method and that based on UV lines would be even more severe if the stellar wind is clumpy. At the same time, our estimate of $\dot{M}$ agrees with that predicted by the moving reversing layer theory by Lucy (2010).

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