In this work, we analyse soft X-ray emission due to mass accretion on to compact stars and its effects on the time-scale to reach chemical equilibrium of eventual surrounding astrophysical ices exposed to that radiation. Reaction time-scales due to soft X-ray in water-rich and pure ices of methanol, acetone, acetonitrile, formic acid, and acetic acid were determined. For accretion rates in the range $\dot{m}=10^{-12}\!-\!10^{-8}\,{\rm M}_\odot$ yr−1 and distances in the range 1–3 LY from the central compact objects, the time-scales lie in the range 10–108 yr, with shorter time-scales corresponding to higher accretion rates. Obtained time-scales for ices at snow-line distances can be small when compared to the lifetime (or age) of the compact stars, showing that chemical equilibrium could have been achieved. Time-scales for ices to reach chemical equilibrium depend on X-ray flux and, hence, on accretion rate, which indicates that systems with low accretion rates may not have reached chemical equilibrium.

中文翻译：

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致密物体周围雪线距离处冰达到化学平衡的时间尺度：中心物体吸积质量的影响

在这项工作中，我们分析了致密恒星的质量吸积导致的软 X 射线发射及其对时间尺度的影响，以达到最终暴露于该辐射的周围天体物理冰的化学平衡。测定了在甲醇、丙酮、乙腈、甲酸和乙酸的富含水和纯冰中的软 X 射线的反应时间尺度。对于 $\dot{m}=10^{-12}\!-\!10^{-8}\,{\rm M}_\odot$ yr−1 范围内的吸积率和范围 1 内的距离–3 LY 来自中央致密天体，时间尺度在 10-108 年的范围内，较短的时间尺度对应于较高的吸积率。与致密恒星的寿命（或年龄）相比，在雪线距离处获得的冰的时间尺度可能很小，这表明可能已经实现了化学平衡。