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arXiv 0802.1773astro-ph
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在(E)UV模式大气通量中的不平衡

Uncertainties in (E)UV model atmosphere fluxes

Thomas Rauch

摘要:

在比较合成光谱计算与两个NLTE模型大气代码,即TMAP和TLUSTY,我们遇到的EUV通量的系统性差异,由于处理水平溶解的压力电离。由于H I莱曼束缚-自由不透明度的代码特定截止频率,可能会出现系统差异。这是TMAP和TLUSTY的情况。这两个代码预测相同的通量水平在波长低于约1500 A的恒星有效温度低于约30000 K只有,如果选择相同的截止频率。在天狼星B的情况下,我们证明了一个不确定性的EUV通量可靠地建模,以挑战理论家,以改善水平溶解的理论。高密度等离子体中的能级溶解理论只适用于氢,应该推广到所有物种。特别是,为了使紫外通量的预测更可靠,应该定义的截止频率的束缚-自由的不透明度。

英文摘要:

During the comparison of synthetic spectra calculated with two NLTE model atmosphere codes, namely TMAP and TLUSTY, we encounter systematic differences in the EUV fluxes due to the treatment of level dissolution by pressure ionization. Systematic differences may occur due to a code-specific cutoff frequency of the H I Lyman bound-free opacity. This is the case for TMAP and TLUSTY. Both codes predict the same flux level at wavelengths lower than about 1500 A for stars with effective temperatures below about 30000K only, if the same cutoff frequency is chosen. In the case of Sirius B, we demonstrate an uncertainty in modeling the EUV flux reliably in order to challenge theoreticians to improve the theory of level dissolution. The theory of level dissolution in high-density plasmas, which is available for hydrogen only should be generalized to all species. Especially, the cutoff frequencies for the bound-free opacities should be defined in order to make predictions of UV fluxes more reliable.

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