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首页> 外文期刊>The Astrophysical journal >TIME-DEPENDENT PHOTOIONIZATION IN A DUSTY MEDIUM. Ⅱ. EVOLUTION OF DUST DISTRIBUTIONS AND OPTICAL OPACITIES
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TIME-DEPENDENT PHOTOIONIZATION IN A DUSTY MEDIUM. Ⅱ. EVOLUTION OF DUST DISTRIBUTIONS AND OPTICAL OPACITIES

机译：灰尘介质中的时间依赖型电离。 Ⅱ。灰尘分布和光学空间的演变

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摘要

The interaction of a radiation field with a dusty medium is a relevant issue in several astrophysical contexts. We use the time-dependent photoionization code in a dusty medium developed by Perna & Lazzati to study the modifications in the dust distribution and the relative optical opacities when a strong X-ray/UV radiation flux propagates into a medium. We find that silicates are preferentially destroyed with respect to graphite, and the extinction curve becomes significantly flatter (hence implying less reddening), with the characteristic bump at 2175 A being highly suppressed because of the destruction of the small graphite grains. This could explain the observational lack of such a feature in gamma-ray-burst afterglow and active galactic nuclei spectra. For a very intense and highly variable source irradiating a compact and dense region, time variability in the optical opacity resulting from dust destruction can be observed on a relatively short timescale. We show that, under these circumstances, monitoring the time variability of the opacity can yield powerful clues to the properties of dust in the environment of the source. In particular, it allows one to break the observational degeneracy as to whether a gray extinction is the result of a low dust-to-gas ratio or of a dust grain distribution that is skewed toward large grains.
机译：在几种天体物理学的背景下，辐射场与尘土介质的相互作用是一个相关问题。我们在Perna＆Lazzati开发的尘土介质中使用时间相关的光电离代码，研究当强X射线/ UV辐射通量传播到介质中时，尘埃分布和相对光学不透明度的变化。我们发现，相对于石墨，硅酸盐优先受到破坏，并且消光曲线变得更加平坦（因此意味着较少的变红），由于小石墨颗粒的破坏，高度抑制了2175 A处的特征凸点。这可以解释在伽马射线爆发余辉和活跃的银河原子核光谱中观察到的缺乏这种特征的现象。对于辐射非常密集和高度可变的紧凑紧凑区域的光源，可以在相对较短的时间范围内观察到由于灰尘破坏而导致的光学不透明性随时间的变化。我们表明，在这种情况下，监视不透明性的时间变化可以提供有关源环境中粉尘特性的有力线索。特别是，它可以打破关于灰烬熄灭是低粉尘比或粉尘颗粒分布偏向大颗粒的结果的观察力退化。

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