超慢旋转磁O型星HD 54879完整自转周期的首次观测
First Observation of the Complete Rotation Period of the Ultra-Slowly Rotating Magnetic O Star HD 54879
AI总结：
本文报告了超慢旋转磁O型星HD 54879完整自转周期的首次观测，推导出其自转周期约7.02年，并基于光谱偏振测量绘制了首张详细磁场图，发现其具有强磁场及显著复杂的拓扑结构。
摘要：
HD 54879是最新发现的磁O型星。先前研究排除了短于7年的自转周期，意味着HD 54879是已知自转第二慢的磁O型星。我们报告了HD 54879的新高分辨率光谱偏振测量结果，证实已观测到完整的恒星自转周期。我们由纵场测量推导出恒星自转周期为P = 2562+63-58 d（约7.02 yr）。HD 54879的径向速度在过去十年的观测中保持稳定。我们探究了由不同元素谱线计算的等值宽度和纵场，得出HD 54879大气可能化学均匀的结论，没有化学分层或横向丰度不均匀的有力证据。我们展示了该恒星首张详细的磁场图，平均表面磁场强度为2954 G，偶极分量为3939 G。场的四极分量含显著磁能（23%）。因此，我们发现HD 54879具有强磁场和显著复杂的拓扑结构。
英文摘要：
HD 54879 is the most recently discovered magnetic O-type star. Previous studies ruled out a rotation period shorter than 7 years, implying that HD 54879 is the second most slowly-rotating known magnetic O-type star. We report new high-resolution spectropolarimetric measurements of HD 54879, which confirm that a full stellar rotation cycle has been observed. We derive a stellar rotation period from the longitudinal magnetic field measurements of P = 2562+63-58 d (about 7.02 yr). The radial velocity of HD 54879 has been stable over the last decade of observations. We explore equivalent widths and longitudinal magnetic fields calculated from lines of different elements, and conclude the atmosphere of HD 54879 is likely chemically homogeneous, with no strong evidence for chemical stratification or lateral abundance nonuniformities. We present the first detailed magnetic map of the star, with an average surface magnetic field strength of 2954 G, and a strength for the dipole component of 3939 G. There is a significant amount of magnetic energy in the quadrupole components of the field (23%). Thus, we find HD 54879 has a strong magnetic field with a significantly complex topology.
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