用高分辨钱德拉谱研究星际介质的物理性质：O K边吸收
Physical properties of the interstellar medium using high-resolution Chandra spectra: O K-edge absorption
摘要：
用一个能确定星际介质物理状态的光电离模型分析了八个低质量星系双星的Chandra高分辨率光谱。特别注意原子数据的准确性。氢柱密度推导出宽带拟合，考虑到堆积效应，并在一般情况下是在良好的协议与以前的结果。氧边缘区域的主要特征是O I和O II K $α$吸收线，其同时拟合导致$\logξ=-2.90$的电离参数和$A_{\rm O}=0.70$的氧丰度的平均值。后者是相对于Grevesse & Sauval（1998）的标准，但Asplund等人（2009）的修订将导致平均丰度值相当接近太阳。低的平均氧柱密度（$N_{\rm O}=9.2 \times 10^{17}$ cm $^{-2}$）表明与低电离参数相关，后者在柱密度比OII/OI和OIII/OI中也很明显，估计小于0.1。除了原子氧之外，我们没有发现任何其他化合物吸收的确凿证据。
英文摘要：
Chandra high-resolution spectra toward eight low-mass Galactic binaries have been analyzed with a photoionization model that is capable of determining the physical state of the interstellar medium. Particular attention is given to the accuracy of the atomic data. Hydrogen column densities are derived with a broadband fit that takes into account pileup effects, and in general are in good agreement with previous results. The dominant features in the oxygen-edge region are O I and O II K$α$ absorption lines whose simultaneous fits lead to average values of the ionization parameter of $\logξ=-2.90$ and oxygen abundance of $A_{\rm O}=0.70$. The latter is relative to the standard by Grevesse & Sauval (1998), but a rescaling with the revision by Asplund et al. (2009) would lead to an average abundance value fairly close to solar. The low average oxygen column density ($N_{\rm O}=9.2 \times 10^{17}$ cm$^{-2}$) suggests a correlation with the low ionization parameters, the latter also being in evidence in the column density ratios OII/OI and OIII/OI that are estimated to be less than 0.1. We do not find conclusive evidence for absorption by any other compound but atomic oxygen.
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