The very massive binary NGC 3603-A1
The very massive binary NGC 3603-A1
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巨大的双星 NGC 3603-A1
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发表时间：
2008
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影响因子：
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通讯作者：
N. St
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作者：
O. Schnurr;O. Schnurr;J. Casoli;J. Casoli;A. Chené;A. Chené;A. F. J. Moffat;N. St
利用VLT/SINFONI（甚大望远镜/摄谱仪近红外综合观测），我们获得了超年轻（1.1亿年）大质量致密星系团NGC 3603核心的三颗中心WN 6 ha星的自适应光学辅助重复近红外光谱。其中一颗恒星NGC 3603-A1是已知的3.77 d双食双星，而另一颗恒星NGC 3603-C是所有已知银河系WR星中最明亮的X射线源之一，这通常是双星的强烈迹象。我们的研究表明，星星C确实是一个8.9-d的二进制，虽然只有WN 6 ha组件是可见的，在我们的光谱，因此，我们暂时分类星星C作为一个SB 1系统。另一方面，A1被发现由两颗光谱类型相似但不一定相同的发射线恒星组成，它们可以在大部分轨道上被跟踪。利用这两个分量的径向速度和先前已知的系统倾角，我们能够推导出A1中两颗恒星的绝对质量。我们发现A1的主分量M1=（116 ± 31）M Ω，次分量M2=（89 ± 16）M Ω。虽然不确定性很大，但A1本质上比WR 20 a亮半等，WR 20 a是目前的记录保持器，分别为83和82 M <$;因此，A1中的主星可能确实是迄今为止质量最大的星星。
Using Very Large Telescope/Spectrograph for INtegral Field Observation in the Near-Infrared (VLT/SINFONI), we have obtained repeated adaptive-optics assisted, near-infrared spectroscopy of the three central WN6ha stars in the core of the very young (∼1 Myr), massive and dense Galactic cluster NGC 3603. One of these stars, NGC 3603-A1, is a known 3.77 d, double-eclipsing binary, while another one, NGC 3603-C, is one of the brightest X-ray sources among all known Galactic WR stars, which usually is a strong indication for binarity. Our study reveals that star C is indeed an 8.9-d binary, although only the WN6ha component is visible in our spectra; therefore, we temporarily classify star C as an SB1 system. A1, on the other hand, is found to consist of two emission-line stars of similar, but not necessarily of identical spectral type, which can be followed over most the orbit. Using radial velocities for both components and the previously known inclination angle of the system, we are able to derive absolute masses for both stars in A1. We find M1= (116 ± 31) M⊙ for the primary and M2= (89 ± 16) M⊙ for the secondary component of A1. While uncertainties are large, A1 is intrinsically half a magnitude brighter than WR20a, the current record holder with 83 and 82 M⊙, respectively; therefore, it is likely that the primary in A1 is indeed the most massive star weighed so far.