IR Studies of the Circumstellar Environs of Evolved Stars

星际介质富含在恒星内部合成的化学元素和在其大气中形成的尘埃颗粒。恒星通过大量的物质流出来完成这种富集，从主序后的缓慢气流，到长时间运行的发光进化恒星，再到新星等爆炸事件。通过观察这些流出物，可以研究化学富集的过程。特别是红外观测将用于提供喷射物中元素的丰度估算，如C、N、O、Ne、Mg、Al和Si，这些元素可用于评估恒星风对星际介质的贡献。对于新星事件，需要在许多波长上对突然的、短暂的活动进行及时的观测。这项研究将提供与质量损失相关的恒星演化阶段的信息，描述星周流出物中天体物理尘埃颗粒的物理特性，并评估新星和发光红外变星对构成星际介质的颗粒和气体的贡献。＊＊＊

AST-0205814PI WoodwardThe interstellar medium is enriched with chemical elements synthesized in the interiors of stars and dust grains formed in their atmospheres. Stars accomplish this enrichment through mass outflows ranging in character from slow winds in post-main sequence, luminous evolved stars that operate over long time scales, to explosive events such as novae. By observing these outflows the process of chemical enrichment can be investigated. In particular IR observations will be carried out to provide abundance estimates for elements in the ejecta, such as C, N, O, Ne, Mg, Al, and Si, that can be used to assess the contributions of stellar winds to the interstellar medium. For a nova event prompt observations of sudden, transient activity at many wavelengths are required. This study will provide information about the stages of stellar evolution that are associated with mass loss, characterize the physical properties of astrophysical dust grains in circumstellar outflows, and assess the contributions that novae and luminous IR variable stars make to the grains and gas that constitute the interstellar medium. ***