在环恒星碳化中多种类型的分布
T L Daulton1, T J Bernatowicz, R S Lewis
1Materials Science Division, Argonne National Laboratory, Argonne IL, 60439-4838, USA. tdaulton@nrlssc.navy.mil
概括
碳化 (SiC) 的天文红外光谱存在争议. 从石中直接分析 presolar SiC 发现只有两个常见的多类型,简化了以前的模型.
科学领域:
- * 天体化学和材料科学.
- *对前太阳颗粒的表征.
- * 恒星进化和核合成.
背景情况:
- *环恒星碳化 (SiC) 的晶体结构受到争论,天文红外光谱表明了多种类型的复杂混合物.
- *以前的研究依赖于间接的光谱分析,导致对恒星外流中形成的实际SiC结构的不确定性.
研究的目的:
- *直接确定环恒星碳化 (SiC) 的多类型分布.
- *为了解决围绕SiC的争议,从天文数据推断出SiC的结晶学类.
- * 了解SiC在恒星环境中的形成条件.
主要方法:
- *使用传输电子显微镜 (TEM) 进行直接结构分析.
- *对从默奇森碳化石中提取的前太阳碳化 (SiC) 颗粒的检查.
- * 在样本中存在的SiC多种类型的识别和量化.
主要成果:
- *只有两种SiC多种类型被确定:立方3C和六角2H.
- * 这两种多种类型的交叉生长也被观察到.
- *观察到的结构简单性与光谱分析表明的多种多样性形成鲜明对比.
结论:
- * 限定的多类型分布归因于环恒星外流中的低压.
- * 在这些环境中,碳化的低凝结温度有利于仅形成3C和2H多种类型.
- * 这一发现简化了我们对进化恒星中SiC形成的理解.
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