arXiv 1902.074752019-02-20astro-ph.EP

原行星盘中的光度爆发化学：超越标准示踪剂

Luminosity outburst chemistry in protoplanetary discs: going beyond standard tracers

Dmitri S. Wiebe, Tamara S. Molyarova, Vitaly V. Akimkin, Eduard I. Vorobyov, Dmitry A. Semenov

备注：: Accepted to MNRAS
DOI：: 10.1093/mnras/stz512

摘要：

探讨了光度爆发对年轻太阳型恒星环境的化学影响。物种根据它们对爆发的反应分为几种类型。第一种和第二种类型意味着只有在爆发期间才发生化学变化（行为略有不同）。这些响应类型主要在靠近恒星的地方观察到，并且是由冰冷的地幔蒸发引起的。然而，地幔在爆发后几乎立即恢复。一个明显的例外是苯冰，它在爆发期间和之后积累在尘埃表面，因此其丰度超过爆发前的数量级。第三种类型的反应主要是看到在光盘周边，并意味着在爆发和保存这些“异常”的丰度几个世纪的丰度变化。这种行为是有机化合物的典型特征，如HCOOCH $_3$、CH $_3$ CN、CH $_2$ CO。它们在暗盘区域的存在可能是过去爆发的表现。CO和CO $_2$只追踪遥远盘区过去的爆发。爆发改变了C/O比，但它很快恢复到爆发前的值，几乎在光盘的任何地方。决定分子组成对爆发的敏感性的一个重要因素是粉尘的粒度分布。如果爆发持续时间短于50年，爆发之间的静止阶段持续时间短于100 kyr，则爆发前阶段和爆发本身的持续时间会影响化学效应。

英文摘要：

The chemical influence of luminosity outbursts on the environments of young solar-type stars is explored. Species are categorised into several types according to their response to the outburst. The first and second types imply chemical changes only during the outburst (with slightly different behaviours). These response types are mostly observed close to the star and are caused by icy mantle evaporation. However, mantles recover after the outburst almost immediately. A notable exception is benzene ice, which is accumulated on dust surfaces during and after the outburst, so that its abundance exceeds the pre-outburst level by orders of magnitude. The third type of response is mostly seen at the disc periphery and implies alteration of abundances during the outburst and preservation of these `abnormal' abundances for centuries. This behaviour is typical of organic compounds, like HCOOCH$_3$, CH$_3$CN, CH$_2$CO. Their presence in the dark disc regions can be a manifestation of the past outburst. CO and CO$_2$ only trace past outbursts at the remote disc regions. The outburst changes the C/O ratio, but it quickly returns to the pre-outburst value almost everywhere in the disc. An important factor determining the sensitivity of molecular composition to the outburst is the dust size distribution. The duration of the pre-outburst stage and of the outburst itself influence the chemical effects, if the burst duration is shorter than 50 yr and the duration of the quiescent phase between the bursts is shorter than 100 kyr.

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摘要：

英文摘要：

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