演化晚期恒星星周包层中的21微米尘埃特征
首发时间:2010-02-09
摘要:21 μm特征是指在一些富碳的原行星状星云的红外光谱中波长约20 μ处观测到的一个较宽的发射谱带特征,它是目前星周包层物质研究的热点问题。到目前为止,一共有16个原行星状星云被证认为21 μm特征源。这16个原行星状星云源的21 μ特征都有相似的谱线轮廓,峰值都位于20.1 μm;中心星都是富碳的F或G型星,贫金属(却有丰富的慢中子过程元素),有很强的红外色余。在过去10年中,人们提出了大量21 μ特征载体的候选物质,主要有:氢化足球烯(C60Hm, m=0∼60)、多环芳香烃(PAH)、氢化无定形碳(HAC)、纳米金刚石颗粒、合成含碳大分子、氨基化合物(特别是尿素)、铁的氧化物(如:γ-Fe2O3、Fe3O4和FeO)、SiS2、纳米TiC团簇、掺杂的SiC颗粒、表面覆盖SiO2幔的SiC颗粒等。但所有这些证认都还没有得到确认。本文概述了21 μm特征的发现及其后续的相关研究,介绍了21 μm特征源的共同特征,比较详细地探讨了人们已提出的该特征载体的候选物质。
关键词: 天体物理学 21 μm特征 星周包层物质 渐近巨星支 后渐近巨星支 恒星
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The 21 micron dust feature in the circumstellar envelope of evolved stars
Abstract:The origin of the so-called 21 micron feature which is prominent in the infrared (IR) spectra of some carbon-rich proto-planetary nebulae (PPNe) has been a mystery since its first detection in 1989. So far, this feature has been detected in 16 PPNe. This feature has a similar intrinsic spectral shape and peaks at the same wavelength (20.1 μm) in all PPNe sources. They are mostly metal-poor, carbon-rich F and G supergiants with IR excesses and overabundant s-process elements. A large number of candidate carriers for this feature have been proposed in the past decade, including hydrogenated fullerenes, polycyclic aromatic hydrocarbon, hydrogenated amorphous carbon, diamonds, synthetic carbonaceous macromolecules, amides (especially urea), iron oxides (γ-Fe2O3, Fe3O4, FeO), SiS2, titanium carbide nanoclusters, doped SiC, and SiC core-SiO2 mantle particles. But none of them has been widely accepted. In this paper we review the observational characteristics of this feature and the proposed candidate materials.
Keywords: astrophysics 21 micron feature circumstellar matter AGB post-AGB stars
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No.4012851207212657****
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