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arXiv 2604.03375astro-ph.GAastro-ph.HE
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星际介质中的硅、硫和铁:GX 340+0的高分辨率X射线光谱研究

Silicon, sulfur and iron in the interstellar medium: a high-resolution X-ray spectral study of GX 340+0

University of Chicago(芝加哥大学);MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology(麻省理工学院卡弗里天体物理学与空间研究所);SRON Netherlands Institute for Space Research(荷兰空间研究所);University of Michigan(密歇根大学);European Space Agency (ESA), European Space Research and Technology Centre (ESTEC)(欧洲空间局(ESA)欧洲空间研究与技术中心(ESTEC))

Daniele Rogantini, Claude Canizares, Elisa Costantini, Liyi Gu, Missagh Mehdipour, Ioanna Psaradaki, Norbert S. Schulz, Sascha T. Zeegers

AI总结:

通过高分辨率X射线光谱研究GX 340+0的星际介质气体和尘埃,确定尘埃成分及硅、硫、铁的吸收特征,揭示尘埃中非晶质橄榄石主导的成分分布。

摘要:

高分辨率X射线光谱学为研究星际介质提供了有力工具,能够直接探测密集环境中尘埃颗粒和原子物种的组成和物理状态。本文研究了沿GX 340+0视线方向的气体和尘埃,利用Chandra/HETG深谱数据,分析了尘埃和气体的X射线吸收精细结构,以及硅、硫和铁K边的光学深度。通过同时拟合这三个边,减少了尘埃成分的退化,发现非晶质橄榄石占尘埃柱密度的约65%,其次是金属铁(约19%)、铁硫化物(pyrrhotite和troilite;约10%)和fayalite(约5%)。从推断的化学计量比,估计约74%的铁与硅酸盐结合,约8%与硫化物结合,约18%与金属铁结合,表明铁主要以富含铁的硅酸盐颗粒形式存在于该视线方向。还检测到S ii吸收并推断硫尘的比例约为35%。此外,还检测到接近Ca和Ar K边的吸收结构,突显了改进原子光电吸收数据的必要性。Chandra/HETG光谱分辨率对于区分硅和硫K边的尘埃和气体贡献至关重要,为高密度区域的尘埃表征提供了基准。

英文摘要:

High-resolution X-ray spectroscopy provides a powerful probe of the interstellar medium (ISM), giving direct access to the composition and physical state of dust grains and atomic species in dense environments. We present a study of the gas and dust along the line of sight to the bright low-mass X-ray binary GX 340+0, which samples higher-density gases in the ISM. Using deep Chandra/HETG spectra, we characterize X-ray absorption fine structure from dust, gas absorption lines, and the optical depths of the Si, S, and Fe K-edges. By fitting these three edges simultaneously, we reduce degeneracies in the dust composition and find that amorphous olivine dominates the fractional contribution among the dust columns ($\sim$65%), followed by metallic iron ($\sim$19%), iron sulfides (pyrrhotite and troilite; $\sim$10%), and fayalite ($\sim$5%), with the remaining species contributing only a few percent in total. From the inferred stoichiometry, we estimate that $\sim$74% of Fe is associated with silicates, $\sim$8% with sulfides, and $\sim$18% with metallic iron, suggesting that Fe is predominantly incorporated in iron rich silicate grains along this sightline. We detect S ii absorption and infer a sulfur dust fraction of $\sim$35%. We also detect absorption structure near the Ca and Ar K edges, highlighting the need for improved atomic photoabsorption data. The Chandra/HETG spectral resolution remains essential to disentangle dust and gas contributions at the Si and S K edges, providing a benchmark for dust characterization in high-density regions in the ISM.

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