Sakurai’s Object revisited: new laboratory data for carbonates and melilites suggest the carrier of 6.9- μ m excess absorption is a carbonate
Sakurai’s Object revisited: new laboratory data for carbonates and melilites suggest the carrier of 6.9- μ m excess absorption is a carbonate
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重新审视樱井的对象：碳酸盐和黄长石的新实验室数据表明，6.9-μm 过量吸收的载体是碳酸盐
DOI：
10.1093/mnras/stac993
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发表时间：
2022
影响因子：
4.8
通讯作者：
Hofmeister, A. M.
中科院分区：
文献类型：
--
作者：
Bowey, J. E.;Hofmeister, A. M.
为了确定在各种密集天文环境中观察到的6.9-−m吸收特征的可能载体(S)，我们给出了黄长石硅酸盐的新的室温-1800-cm−-1谱和3个随机取向的细粒碳酸盐的600-2000-cmμ-1谱。我们聚焦于低质量的后渐近巨星分支恒星樱井的天体，自20世纪90年代的一次喷发事件以来，它一直在形成大量的碳质尘埃。大的黄长石颗粒不能对6.9-μm的吸收特征负责，因为实验室光谱中类似形状的特征是由非常低的(0.1% 质量分数)碳酸盐污染产生的，这在其他波长没有检测到。由于碳酸盐中6.9-μm特征的高频带强度，我们得出结论，碳酸盐具有天文上的6.9-μm特征。在樱井天体的模型中用碳酸盐取代黄长石，改善了对6-7-μmSpitzer谱的拟合，而不会显著改变鲍伊之前模型的其他结论，只是这一特征与陨石中黄长石的丰度之间没有联系。使用镁砂(碳酸镁)，25μm尺寸的碳化硅颗粒的丰度提高了10-50% %，并得到了更好的约束。碳酸盐粉尘的质量与多环芳烃粉尘的质量相似。现有的实验表明，碳酸盐在700℃以下是稳定的；然而，很难确定这些实验对天文环境的适用性，还需要更多的研究。
We present new room-temperature 1100–1800-cm−1spectra of melilite silicates and 600–2000-cm−1spectra of three randomly orientated fine-grained carbonates to determine the possible carrier(s) of a 6.9-μm absorption feature observed in a variety of dense astronomical environments, including young stellar objects and molecular clouds. We focus on the low-mass post-asymptotic giant branch star Sakurai’s Object, which has been forming substantial quantities of carbonaceous dust since an eruptive event in the 1990s. Large melilite grains cannot be responsible for the 6.9-μm absorption feature because the similarly shaped feature in the laboratory spectrum was produced by very low (0.1 per cent by mass) carbonate contamination, which was not detected at other wavelengths. Due to the high band strength of the 6.9-μm feature in carbonates, we conclude that carbonates carry the astronomical 6.9-μm feature. Replacement of melilite with carbonates in models of Sakurai’s Object improves fits to the 6–7-μmSpitzerspectra without significantly altering other conclusions of Bowey’s previous models except that there is no link between the feature and the abundance of melilite in meteorites. With magnesite (MgCO3), the abundance of 25-μm-sized SiC grains is increased by 10–50 per cent and better constrained. The mass of carbonate dust is similar to the mass of polycyclic aromatic hydrocarbon dust. Existing experiments suggest that carbonates are stable below 700 K; however, it is difficult to ascertain the applicability of these experiments to astronomical environments, and more studies are required.