Magnetic cycles of the planet-hosting star τ Bootis – II. A second magnetic polarity reversal
Magnetic cycles of the planet-hosting star τ Bootis – II. A second magnetic polarity reversal
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行星主恒星 τ Bootis 的磁循环 – II。
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
Gordon A. H. Walker
中科院分区：
文献类型：
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作者：
R. Fares;J. Donati;C. Moutou;D. Bohlender;C. Català;M. Deleuil;E. Shkolnik;A. Cameron;M. Jardine;Gordon A. H. Walker
在本文中，我们分别使用加拿大-法国-夏威夷望远镜（CFHT）和伯纳德·利奥特望远镜（TBL）的ESPaDOnS和Narval分光偏振计，提出了对行星主恒星Bootis进行新的分光偏振观测。 2008年，我们在三个历元探测到了恒星的磁场。它是一个只有几个高斯的弱磁场，在一月的主要环形成分和六月和七月的主要极向成分之间振荡。 2007 年 6 月，观测到相对于磁拓扑的磁极性反转。这是两年内在这颗恒星上观测到的第二次此类反转，表明 Boo 的磁周期约为 2 年。这是首次探测到太阳以外恒星的磁周期。这颗近距离大质量行星在恒星短活动周期中的作用受到质疑。 � Boo 具有很强的差动自转，这是具有浅对流包层的恒星的常见趋势。在纬度40°处，恒星表面层的自转周期为3.31天，等于轨道周期。同步表明，行星引起的潮汐效应可能足够强大，至少迫使薄对流包层同步旋转。 Boo 显示了 Ca II H & K 和 H 在整个晚上以及夜间时间尺度上的变化。我们没有检测到恒星活动的增强可能与行星的合相有关。需要进一步的数据来得出关于地球活动增强的结论。
In this paper, we present new spectropolarimetric observations of the planet- hosting starBootis, using ESPaDOnS and Narval spectropolarimeters at Canada- France-Hawaii Telescope (CFHT) and Telescope Bernard Lyot (TBL), respectively. We detected the magnetic field of the star at three epochs in 2008. It is a weak magnetic field of only a few Gauss, oscillating between a predominant toroidal com- ponent in January and a dominant poloidal component in June and July. A magnetic polarity reversal was observed relative to the magnetic topology in June 2007. This is the second such reversal observed in two years on this star, suggesting thatBoo has a magnetic cycle of about 2 years. This is the first detection of a magnetic cycle for a star other than the Sun. The role of the close-in massive planet in the short activity cycle of the star is questioned. � Boo has strong differential rotation, a common trend for stars with shallow convective envelope. At latitude 40 ◦ , the surface layer of the star rotates in 3.31 d, equal to the orbital period. Synchronization suggests that the tidal effects induced by the planet may be strong enough to force at least the thin convective envelope into corotation. � Boo shows variability in the Ca II H & K and Hthroughout the night and on a night to night time scale. We do not detect enhancement in the activity of the star that may be related to the conjunction of the planet. Further data is needed to conclude about the activity enhancement due to the planet.