Discovery of a strong magnetic field on the O star HD 191612: new clues to the future of θ 1 Orionis C? ⋆
Discovery of a strong magnetic field on the O star HD 191612: new clues to the future of θ 1 Orionis C? ⋆
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O星HD 191612上发现强磁场：猎户座θ 1 C未来的新线索？
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
J. Landstreet
中科院分区：
文献类型：
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作者：
J. Donati;I. Howarth;J. Bouret;Pascal Petit;C. Català;J. Landstreet
从与ESPaDOnS分光偏振仪，最近安装在3.6米加拿大-法国-夏威夷望远镜的观测，我们报告发现了一个强磁场的？p光谱变星HD 191612 -唯一已知的第二颗磁性O型星星（继1 Ori C之后）。四个晚上观测到的塞曼信号的稳定性，以及线轮廓的非旋转形状，表明HD 191612的旋转周期明显长于先前提出的9-d值。我们认为，最近确定的538-d光谱变化周期是旋转周期，在这种情况下，观察到的视线磁场为220 ± 38 G意味着一个大尺度场（假设偶极），极强度约为1.5 kG。如果得到证实，这种情况表明HD 191612本质上是近ZAMS磁性O星星-1 Ori C的进化版本，但具有更强的磁场（在与-1 Ori C相似的年龄时约为15 kG）。我们认为，HD 191612的旋转速度，这是非常慢的公认的O星标准，可能是由于角动量耗散通过磁约束风。
From observations made with the ESPaDOnS spectropolarimeter, recently installed on the 3.6-m Canada–France–Hawaii Telescope, we report the discovery of a strong magnetic field in the Of?p spectrum variable HD 191612 – only the second known magnetic O star (following � 1 Ori C). The stability of the observed Zeeman signature over four nights of observation, together with the non-rotational shape of line profiles, argue that the rotation period of HD 191612 is significantly longer than the 9-d value previously proposed. We suggest that the recently identified 538-d spectral-variability period is the rotation period, in which case the observed line-of-sight magnetic field of 220 ± 38 G implies a large-scale field (assumed dipolar) with a polar strength of about 1.5 kG. If confirmed, this scenario suggests that HD 191612 is, essentially, an evolved version of the near-ZAMS magnetic O star � 1 Ori C, but with an even stronger field (about 15 kG at an age similar to that of � 1 Ori C). We suggest that the rotation rate of HD 191612, which is exceptionally slow by accepted O-star standards, could be due to angular-momentum dissipation through a magnetically confined wind.