银河系未分类的B[e]星HD 50138。I.可能的新壳阶段
The galactic unclassified B[e] star HD 50138. I. A possible new shell phase
摘要：
观测到的HD 50138的光谱变化导致不同的作者将其分为非常广泛的光谱类型和光度类别（从B5到A0和III到Ia），并在不同的演化阶段将其分为HAeBe星或经典Be星。目的：基于1999年和2007年与光度分析相关的新的高分辨率光学光谱数据，这项工作的目的是为这颗未分类的南部B[e]星及其星际消光提供一个深层次的光谱描述和一组新的参数。研究方法：从我们的高分辨率光学光谱数据分离8年，我们执行详细的光谱描述，呈现所看到的变化，并讨论其可能的起源。通过考虑星周物质的尘埃和电离盘的影响，我们推导出了HD 50138的星际消光。基于光度数据从文献和新的依巴谷距离，我们得到了一组修订后的参数HD 50138。结果：由于光谱的变化，我们初步认为，一个新的壳相可能已经发生之前，我们在2007年的观测。我们发现HD 50138的色余值为E（B-V）= 0.08等，根据光度分析，我们认为HD 50138是一颗B6-7 III-V星。还提供了不同的进化方案的讨论。
英文摘要：
The observed spectral variation of HD 50138 has led different authors to classify it in a very wide range of spectral types and luminosity classes (from B5 to A0 and III to Ia) and at different evolutionary stages as either HAeBe star or classical Be. Aims: Based on new high-resolution optical spectroscopic data from 1999 and 2007 associated to a photometric analysis, the aim of this work is to provide a deep spectroscopic description and a new set of parameters for this unclassified southern B[e] star and its interstellar extinction. Methods: From our high-resolution optical spectroscopic data separated by 8 years, we perform a detailed spectral description, presenting the variations seen and discussing their possible origin. We derive the interstellar extinction to HD 50138 by taking the influences of the circumstellar matter in the form of dust and an ionized disk into account. Based on photometric data from the literature and the new Hipparcos distance, we obtain a revised set of parameters for HD 50138. Results: Because of the spectral changes, we tentatively suggest that a new shell phase could have taken place prior to our observations in 2007. We find a color excess value of E(B-V) = 0.08 mag, and from the photometric analysis, we suggest that HD 50138 is a B6-7 III-V star. A discussion of the different evolutionary scenarios is also provided.
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