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arXiv 1012.1875astro-ph.SR
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银河系和麦哲伦星云中最明亮的恒星

The most luminous stars in the Galaxy and the Magellanic Clouds

Wolf-Rainer Hamann, Andreas Barniske, Adriane Liermann, Lidia M. Oskinova, Diana Pasemann, Ute Ruehling

摘要:

一些沃尔夫-拉叶星被发现有非常高的热光度(超过1000000太阳)。我们采用波茨坦Wolf-Rayet(PoWR)模式大气的光谱分析,从而产生的测热校正。距离和星际变红也进入了光度估计。在银河系的恒星中,有一组非常明亮的WNL恒星(即氮序列的晚期亚型的WR恒星,其大气中的氢被耗尽,但并非不存在)。它们的距离往往是不确定性的主要来源。通过K波段光谱,我们在银河系中心区域发现了一颗非常明亮的恒星($\log L/L_\odot = 6.5$),由于其周围尘埃星云的形状,我们将其命名为牡丹星。在大麦云星云(LMC)中也发现了一组类似的非常明亮的WNL恒星。在小麦哲伦星云(SMC)中,大多数WR星都存在于双星系统中。SMC中的单个WNL恒星并不十分明亮。我们的结论是,一个显着的数量非常明亮的WNL恒星存在于银河系和LMC。当初始质量超过60 $M_\odot$时,它们显然直接进化到WNL阶段,而没有事先偏移到HRD的红色一侧。在低金属丰度的SMC中,双星通道可能是WR星形成的主要通道。

英文摘要:

Some of the Wolf-Rayet stars are found to have very high bolometric luminosities (more than 1000000 solar). We employ the Potsdam Wolf-Rayet (PoWR) model atmospheres for their spectral analysis, which yields the bolometric corrections. Distance and interstellar reddening also enter the luminosity estimates. Among the Galactic stars, there is a group of very luminous WNL stars (i.e. WR stars of late subtype from nitrogen sequence with hydrogen being depleted in their atmospheres, but not absent). Their distances are often the major source of uncertainty. From K-band spectroscopy we found a very luminous star ($\log L/L_\odot = 6.5$) in the Galactic center region, which we termed the Peony Star because of the form of its surrounding dusty nebula. A similar group of very luminous WNL stars is found in the Large Magellanic Cloud (LMC). In the Small Magellanic Cloud (SMC) the majority of WR stars resides in binary systems. The single WNL stars in the SMC are not very luminous. We conclude that a significant number of very luminous WNL stars exist in the Galaxy and the LMC. With initial masses above 60$M_\odot$, they apparently evolved directly to the WNL stage without a prior excursion to the red side of the HRD. At the low metallicity of the SMC, the binary channel may be dominant for the formation of WR stars.

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