M3（NGC 5272）中紫外亮星vZ 1128的FUSE、STIS和凯克光谱分析
FUSE, STIS, and Keck spectroscopic analysis of the UV-bright star vZ 1128 in M3 (NGC 5272)
摘要：
我们提出了一个光谱分析的紫外线明亮的恒星VZ 1128在M3的基础上与远紫外线光谱探测器（FUSE），空间望远镜成像光谱仪（STIS），和凯克HIRES阶梯光栅光谱仪的观测。通过用非LTE H-He模型拟合凯克谱中的H I、He I和He II线，我们得到Teff = 36，600 K，log g = 3.95，log N（He）/N（H）=-0.84。恒星的FUSE和STIS光谱显示光球层吸收了C、N、O、Al、Si、P、S、Fe和Ni。没有观察到来自铁峰以外的元素的恒星特征。N V 1240双重谱线的两个分量都具有P~天鹅座轮廓，表明存在弱的星风，但没有看到其它的星风特征。这颗恒星的光球丰度似乎自它离开红巨星分支（RGB）以来变化不大。它的C、N、O、Al、Si、Fe和Ni的丰度与M3中红巨星的公布值一致，C、N和O的相对丰度遵循在星团RGB上看到的趋势。特别是，它的低碳丰度表明，该恒星在第三次挖掘开始之前离开了渐近巨星分支。
英文摘要：
We present a spectral analysis of the UV-bright star vZ 1128 in M3 based on observations with the Far Ultraviolet Spectroscopic Explorer (FUSE), the Space Telescope Imaging Spectrograph (STIS), and the Keck HIRES echelle spectrograph. By fitting the H I, He I, and He II lines in the Keck spectrum with non-LTE H-He models, we obtain Teff = 36,600 K, log g = 3.95, and log N(He)/N(H) = -0.84. The star's FUSE and STIS spectra show photospheric absorption from C, N, O, Al, Si, P, S, Fe, and Ni. No stellar features from elements beyond the iron peak are observed. Both components of the N V 1240 doublet exhibit P~Cygni profiles, indicating a weak stellar wind, but no other wind features are seen. The star's photospheric abundances appear to have changed little since it left the red giant branch (RGB). Its C, N, O, Al, Si, Fe, and Ni abundances are consistent with published values for the red-giant stars in M3, and the relative abundances of C, N, and O follow the trends seen on the cluster RGB. In particular, its low C abundance suggests that the star left the asymptotic giant branch before the onset of third dredge-up.
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