OB星（BOB）中的B场：探测O9 .7 V星HD54879中的强磁场
B fields in OB stars (BOB): Detection of a strong magnetic field in the O9.7 V star HD54879
摘要：
在大质量恒星中检测到的磁星数量很少;然而，磁场在恒星演化中所起的作用不容忽视。对于低质量的B星，已经确定了谱线轮廓变化、表面化学丰度的增强/减少和磁场之间的联系，但是对于O型域，这几乎是未探索的。基于FORS 2和HARPS光谱偏振数据，我们提出了在HD 54879，一个缓慢旋转的O 9.7 V的单一恒星的磁场的第一次检测。使用两个独立的和不同的技术，我们得到了坚定的检测表面平均纵向磁场的最大幅度约为600 G，模量。用恒星大气程序FASTWIND对这颗恒星进行了定量光谱分析，得到了它的有效温度和表面重力分别为33000 $\pm1000$ K和4.0 $\pm0.1$ dex。碳、氮、氧、硅和镁的丰度略低于太阳，但在误差范围内是相容的。我们调查线轮廓的变化，在HD 54879补充我们的光谱与光谱数据，从其他最近的OB-star调查。光球线在2009年至2014年之间保持不变的形状，尽管H $α$显示出可变的发射。H $α$的发射对于标准的O9.7 V来说太强了，可能与磁场和星周物质的存在有关。其正常的化学成分和没有光球线轮廓变化使HD 54879成为迄今为止探测到的最强磁性，不变的单颗O星。
英文摘要：
The number of magnetic stars detected among massive stars is small; nevertheless, the role played by the magnetic field in stellar evolution cannot be disregarded. Links between line profile variability, enhancements/depletions of surface chemical abundances, and magnetic fields have been identified for low-mass B-stars, but for the O-type domain this is almost unexplored. Based on FORS2 and HARPS spectropolarimetric data, we present the first detection of a magnetic field in HD54879, a single slowly rotating O9.7 V star. Using two independent and different techniques we obtained the firm detection of a surface average longitudinal magnetic field with a maximum amplitude of about 600 G, in modulus. A quantitative spectroscopic analysis of the star with the stellar atmosphere code FASTWIND results in an effective temperature and a surface gravity of 33000$\pm1000$ K and 4.0$\pm0.1$ dex. The abundances of carbon, nitrogen, oxygen, silicon, and magnesium are found to be slightly lower than solar, but compatible within the errors. We investigate line-profile variability in HD54879 by complementing our spectra with spectroscopic data from other recent OB-star surveys. The photospheric lines remain constant in shape between 2009 and 2014, although H$α$ shows a variable emission. The H$α$ emission is too strong for a standard O9.7 V and is probably linked to the magnetic field and the presence of circumstellar material. Its normal chemical composition and the absence of photospheric line profile variations make HD54879 the most strongly magnetic, non-variable single O-star detected to date.
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