SMC团簇中H α发射线天体的无狭缝光谱测量
A slitless spectroscopic survey for Halpha emission-line objects in SMC clusters
摘要：
本文检查的作用，金属丰度和演化年龄的出现，所谓的Be现象。获得了覆盖大部分小麦哲伦云的无狭缝CCD光谱。对于比环境连续谱强两倍的H α线发射，主层序上的光谱类型B2/B3的测量是完整的。在84个疏散星团中搜索了4437颗恒星的8120个光谱。发现了370颗发射线恒星，其中至少有231颗在主序星附近。其中176个的光度测定可以在OGLE数据库中找到。为了与金属丰度较高的环境进行比较，使用了McSwain和Gies（2005年）光度测量的银河样本。在早期的光谱子类型中，Be星在SMC中比在银河系中更常见3-5倍。光谱类型的分布在两个星系中是相似的，即不强烈依赖于金属丰度。Be星的比例似乎不随局部恒星密度而变化。Be现象主要发生在主序星演化的末期（这种趋势在SMC中可能更为明显）;但一些Be星已经形成了Be星的特征。在所有的概率，分数临界角旋转速率，\omc，是一个主要的参数控制的Be现象的发生。如果Be特征是在演化过程中才获得的，那么关键的环境是\omc的演化，它不仅依赖于金属丰度，而且对不同的质量范围有不同的依赖性。
英文摘要：
This paper checks on the roles of metallicity and evolutionary age in the appearance of the so-called Be phenomenon. Slitless CCD spectra were obtained covering the bulk of the Small Magellanic Cloud. For Halpha line emission twice as strong as the ambient continuum, the survey is complete to spectral type B2/B3 on the main sequence. About 8120 spectra of 4437 stars were searched for emission lines in 84 open clusters. 370 emission-line stars were found, among them at least 231 near the main sequence. For 176 of them, photometry could be found in the OGLE database. For comparison with a higher-metallicity environment, the Galactic sample of the photometric Halpha survey by McSwain & Gies (2005) was used. Among early spectral sub-types, Be stars are more frequent by a factor 3-5 in the SMC than in the Galaxy. The distribution with spectral type is similar in both galaxies, i.e. not strongly dependent on metallicity. The fraction of Be stars does not seem to vary with local star density. The Be phenomenon mainly sets in towards the end of the main-sequence evolution (this trend may be more pronounced in the SMC); but some Be stars already form with Be-star characteristics. In all probability, the fractional critical angular rotation rate, \omc, is one of the main parameters governing the occurrence of the Be phenomenon. If the Be character is only acquired during the course of evolution, the key circumstance is the evolution of \omc, which not only is dependent on metallicity but differently so for different mass ranges.
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