Luminous and Variable Stars in M31 and M33. IV. Luminous Blue Variables, Candidate LBVs, B[e] Supergiants, and the Warm Hypergiants: How to Tell Them Apart
Luminous and Variable Stars in M31 and M33. IV. Luminous Blue Variables, Candidate LBVs, B[e] Supergiants, and the Warm Hypergiants: How to Tell Them Apart
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M31 和 M33 中的发光星和变星。
DOI：
10.3847/1538-4357/aa582e
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
David Hahn
中科院分区：
文献类型：
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作者：
R. Humphreys;M. Gordon;John C. Martin;K. Weis;David Hahn
在这一系列的论文中，我们介绍了对附近螺旋线M31和M33中的发光恒星进行的光谱调查的结果。在这里，我们展示了另外132颗恒星的光谱。大多数都有发射线光谱，包括发光蓝星(LBV)和候选LBV、Fe II发射线恒星、B[e]超巨星和暖超巨星。这些天体中的许多在光谱上是相似的，经常相互混淆。我们考察了它们的异同，并提出了以下准则，可用于在未来的工作中帮助区分这些恒星。(1)B[e]超巨星的光谱具有[O I]和[Fe II]的发射线。大多数光谱确认的SGB[e]恒星的光谱能量分布(SED)中也有温暖的星际尘埃。(2)确认的LBV在其光谱中没有[O I]发射线。一些LBV有[Fe II]发射线，但不是全部。他们的SED在近红外线显示自由发射，但没有证据表明有温暖的尘埃。它们最重要、也是最具决定性的特征是S的多尔型变异性。(3)暖超巨星在光谱上类似于密集风状态下的LBV和B[e]超巨星。然而，它们非常尘土飞扬。有些恒星的光谱中有[Fe II]和[O I]发射，就像SGB[e]星一样，但它们的A型和F型吸收线谱是不同的。相比之下，B[e]超巨谱有很强的连续性，几乎没有明显的吸收线。候选LBV应该具有已确认的LBV的光谱特征，这些LBV具有低流出速度和缺乏温暖的星际尘埃。
In this series of papers we have presented the results of a spectroscopic survey of luminous stars in the nearby spirals M31 and M33. Here, we present spectroscopy of 132 additional stars. Most have emission-line spectra, including luminous blue variables (LBVs) and candidate LBVs, Fe ii emission line stars, the B[e] supergiants, and the warm hypergiants. Many of these objects are spectroscopically similar and are often confused with each other. We examine their similarities and differences and propose the following guidelines that can be used to help distinguish these stars in future work. (1) The B[e] supergiants have emission lines of [O i] and [Fe ii] in their spectra. Most of the spectroscopically confirmed sgB[e] stars also have warm circumstellar dust in their spectral energy distributions (SEDs). (2) Confirmed LBVs do not have the [O i] emission lines in their spectra. Some LBVs have [Fe ii] emission lines, but not all. Their SEDs show free–free emission in the near-infrared but no evidence for warm dust. Their most important and defining characteristic is the S Dor-type variability. (3) The warm hypergiants spectroscopically resemble the LBVs in their dense wind state and the B[e] supergiants. However, they are very dusty. Some have [Fe ii] and [O i] emission in their spectra like the sgB[e] stars, but are distinguished by their A- and F-type absorption-line spectra. In contrast, the B[e] supergiant spectra have strong continua and few if any apparent absorption lines. Candidate LBVs should share the spectral characteristics of the confirmed LBVs with low outflow velocities and the lack of warm circumstellar dust.