Equivalent width, shape and proper motion of the iron fluorescent line emission from the molecular clouds as an indicator of the illuminating source X-ray flux history
Equivalent width, shape and proper motion of the iron fluorescent line emission from the molecular clouds as an indicator of the illuminating source X-ray flux history
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分子云发射的铁荧光线的等效宽度、形状和自行作为照明源 X 射线通量历史的指标
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发表时间：
1998
期刊：
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通讯作者：
E.Churazov
中科院分区：
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作者：
R.Sunyaev;E.Churazov
对平行于银面延伸的8-22 keV能量范围内的散射辐射的观测（Sunyaev et al. 1993）和对银河系中心区域一些巨大分子云（例如Sgr B2）具有1 keV等效宽度的强6.4 keV荧光线的探测（Koyama 1994）表明，这些云的中性物质被（或曾经）被强大的x射线辐射照射，从而产生了再处理辐射。这种辐射的来源仍然未知。靠近Sgr B2星云的瞬变源或银河系中心超大质量黑洞的x射线短爆发是两个主要的候选对象。我们认为，结合非常高的灵敏度和优异的能量和角分辨率的新一代x射线望远镜将能够区分这两种可能性，研究Sgr B2和该地区其他分子云的表面亮度分布、等效宽度和荧光线形状的时间依赖变化。我们还注意到，在遥远的agn的光谱中，在6.4 keV线附近探测到广泛而复杂的结构，这些结构现在是x射线弱的，可能证明这些物体的中心引擎在过去存在剧烈的活动。对线形的精确测量可以提供自爆发以来经过的时间的信息。荧光辐射波前的适当运动（上或下）可以提供有关光源位置的额外信息。对所描述的效应的观测可以提供关于Sgr B2和其他巨大分子云内部物质分布的独特信息。
Observations of the diffuse emission in the 8–22 keV energy range, elongated parallel to the Galactic plane (Sunyaev et al. 1993) and detection of the strong 6.4 keV fluorescent line with ∼ 1 keV equivalent width from some giant molecular clouds (e.g. Sgr B2) in the Galactic Centre region (Koyama 1994) suggest that the neutral matter of these clouds is (or was) illuminated by powerful X-ray radiation, which gave rise to the reprocessed radiation. The source of this radiation remains unknown. Transient source close to the Sgr B2 cloud or short outburst of the X-ray emission from supermassive black hole at the Galactic Centre are the two prime candidates under consideration. We argue that new generation of X-ray telescopes combining very high sensitivity and excellent energy and angular resolutions would be able to discriminate between these two possibilities studying time dependent changes of the morphology of the surface brightness distribution, the equivalent width and the shape of the fluorescent line in the Sgr B2 and other molecular clouds in the region. We note also that detection of broad and complex structures near the 6.4 keV line in the spectra of distant AGNs, which are X–ray weak now, may prove the presence of violent activity of the central engines of these objects in the past. Accurate measurements of the line shape may provide an information on the time elapsed since the outburst. Proper motion (super or subluminal) of the fluorescent radiation wave front can give additional information on the location of the source. Observations of the described effects can provide unique information on the matter distribution inside Sgr B2 and other giant molecular clouds.