DISCOVERY OF THE FIRST B[e] SUPERGIANTS IN M 31
DISCOVERY OF THE FIRST B[e] SUPERGIANTS IN M 31
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DOI：
10.1088/2041-8205/780/1/l10
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发表时间：
2013-12
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影响因子：
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通讯作者：
M. Kraus;L. Cidale;M. Arias;M. Oksala;M. Fernandes
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作者：
M. Kraus;L. Cidale;M. Arias;M. Oksala;M. Fernandes
B[e]超巨星（B[e] SG）是大质量恒星后主序星演化的过渡天体。迄今为止，在银河系和麦哲伦星云中已知的B[e] SG数量很少，这表明这个演化阶段很短。然而，在这一阶段发生的强烈的非球面质量损失，这导致了环或盘状结构的形成，以及与SN 1987 A可能的祖先的相似性，强调了B[e] SG对星际介质动力学以及恒星和银河系化学演化的重要性。天体的数量及其在不同金属丰度下的质量损失行为是恒星和星系演化计算准确预测的基本要素。然而，B[e] SG并不容易识别，因为它们在静止（热）阶段与亮蓝变星（LBV）有许多共同的特征。我们提出了中等分辨率的近红外K波段光谱的四颗恒星在M 31，这已被分配一个热LBV（候选人）的地位。应用诊断，最近开发的热LBV区分B[e] SG，我们分类为真正的LBV的对象，其中之一，目前在爆发。此外，我们还根据光谱中检测到的强CO带发射和这类恒星典型的红外色，将2MASS J00441709+4119273和2MASS J00452257+4150346确定为M 31中的第一批B[e] SG。
B[e] supergiants (B[e]SGs) are transitional objects in the post-main sequence evolution of massive stars. The small number of B[e]SGs known so far in the Galaxy and the Magellanic Clouds indicates that this evolutionary phase is short. Nevertheless, the strong aspherical mass loss occurring during this phase, which leads to the formation of rings or disk-like structures, and the similarity to possible progenitors of SN1987 A emphasize the importance of B[e]SGs for the dynamics of the interstellar medium as well as stellar and galactic chemical evolution. The number of objects and their mass-loss behavior at different metallicities are essential ingredients for accurate predictions from stellar and galactic evolution calculations. However, B[e]SGs are not easily identified, as they share many characteristics with luminous blue variables (LBVs) in their quiescent (hot) phase. We present medium-resolution near-infrared K-band spectra for four stars in M 31, which have been assigned a hot LBV (candidate) status. Applying diagnostics that were recently developed to distinguish B[e]SGs from hot LBVs, we classify two of the objects as bonafide LBVs; one of them currently in outburst. In addition, we firmly classify the two stars 2MASS J00441709+4119273 and 2MASS J00452257+4150346 as the first B[e]SGs in M 31 based on strong CO band emission detected in their spectra, and infrared colors typical for this class of stars.