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arXiv 0812.4605astro-ph
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寻找O7 III星英仙座xi的磁场

Search for the magnetic field of the O7.5 III star xi Persei

H. F. Henrichs, R. S. Schnerr, J. A. de Jong, L. Kaper, J. -F. Donati, C. Catala

摘要:

周期性的风变率是OB星普遍存在但尚未解释的特征。O7.5 III(n)((f))星英仙座xi是北半球最明亮的代表。由于其突出的周期性风属性在旋转时间尺度(2或4天)上变化,该恒星已经很长一段时间是一个重要的磁性候选者。作为这种神秘行为的原因,非径向脉动和/或表面磁场被提出。我们提出了一个初步的报告,我们试图检测一个磁场在这颗星的高分辨率测量获得的分光偏振计Narval在TBL,法国在2个观测运行的5个晚上在2006年和2007年的5个晚上。即使暴露时间尽可能长,也只能获得上限。如果恒星有磁场,它的表面强度应该小于300 G。这也足以对星风造成不小的干扰。从我们的新数据来看,已知的非径向脉动的振幅似乎在不到一年的时间内发生了变化,这需要进一步的调查。

英文摘要:

Cyclical wind variability is an ubiquitous but as yet unexplained feature among OB stars. The O7.5 III(n)((f)) star xi Persei is the brightest representative of this class on the Northern hemisphere. As its prominent cyclical wind properties vary on a rotational time scale (2 or 4 days) the star has been already for a long time a serious magnetic candidate. As the cause of this enigmatic behavior non-radial pulsations and/or a surface magnetic field are suggested. We present a preliminary report on our attempts to detect a magnetic field in this star with high-resolution measurements obtained with the spectropolarimeter Narval at TBL, France during 2 observing runs of 5 nights in 2006 and 5 nights in 2007. Only upper limits could be obtained, even with the longest possible exposure times. If the star hosts a magnetic field, its surface strength should be less than about 300 G. This would still be enough to disturb the stellar wind significantly. From our new data it seems that the amplitude of the known non-radial pulsations has changed within less than a year, which needs further investigation.

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