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arXiv 1201.4716astro-ph.SR
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O型星风产生的X射线谱的全球模拟

Global modelling of X-ray spectra produced in O-type star winds

A. Hervé, G. Rauw, Y. Nazé, A. Foster

摘要:

O型恒星的高分辨率X射线光谱显示,风的吸收比预期的要少,因为风是平滑的,具有传统的质量损失率。已经提出了各种解决方案,包括多孔风,光学厚团块或整体减少质量损失率。后者对恒星的演化有很大的影响。我们的最终目标是用多温度等离子体模型分析O型星的高分辨率X射线谱,以确定重要的风参数,如质量损失率、CNO丰度和风中X射线温度等离子体分布。在这种情况下,我们正在开发一个建模工具来计算合成X射线光谱。我们目前,在这里,这样的工作所需的主要成分和物理。我们的代码使用AtomDB发射率计算热等离子体的固有发射率以及CMFGEN模型大气代码来评估冷风的不透明度。继恒星风碎裂的两种形式主义之间的比较,我们介绍,第一次在X射线,一个稀薄的团间介质的影响。然后,我们探讨了不同的模型参数对X射线光谱的定量影响,如X射线发射等离子体在风中的位置。这是第一次,我们表明,两种形式的恒星风碎片产生不同的结果,虽然个别线的差异很小,可能无法测试与当前一代的X射线望远镜。作为我们的方法的一个例子,我们比较了各种合成线的轮廓,观察到的O VIII λ 18.97线的光谱中的Puppis。我们说明了不同的参数组合实际上可以导致同一形态的一条线,强调需要分析整个频谱时,试图约束风的参数一致的方式。

英文摘要:

High-resolution X-ray spectra of O-type stars revealed less wind absorption than expected from smooth winds with conventional mass-loss rates. Various solutions have been proposed, including porous winds, optically thick clumps or an overall reduction of the mass-loss rates. The latter has a strong impact on the evolution of the star. Our final goal is to analyse high resolution X-ray spectra of O-type stars with a multi temperature plasma model in order to determine crucial wind parameters such as the mass loss rate, the CNO abundances and the X-ray temperature plasma distribution in the wind. In this context we are developing a modelling tool to calculate synthetic X-ray spectra. We present, here, the main ingredients and physics necessary for a such work. Our code uses the AtomDB emissivities to compute the intrinsic emissivity of the hot plasma as well as the CMFGEN model atmosphere code to evaluate the opacity of the cool wind. Following the comparison between two formalisms of stellar wind fragmentation, we introduce, for the first time in X-rays, the effects of a tenuous inter-clump medium. We then explore the quantitative impact of different model parameters on the X-ray spectra such as the position in the wind of the X-ray emitting plasma. For the first time, we show that the two formalisms of stellar wind fragmentation yield different results, although the differences for individual lines are small and can probably not be tested with the current generation of X-ray telescopes. As an illustration of our method, we compare various synthetic line profiles to the observed O VIII λ 18.97Å line in the spectrum of ζ Puppis. We illustrate how different combinations of parameters can actually lead to the same morphology of a single line, underlining the need to analyse the whole spectrum in a consistent way when attempting to constrain the parameters of the wind.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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