MOST探测到牧夫座τ可能由其行星伴星引起的变化
MOST detects variability on tau Bootis possibly induced by its planetary companion
摘要：
在51个Peg型系统中，母星和巨行星伴星之间可能的相互作用引起了相当大的兴趣。我们表明，从MOST卫星测光和钙II K线发射，有一个持久的，可变的区域的表面上的τ Boo A跟踪其巨大的行星伴侣约440行星的革命和谎言~ 68度（φ =0.8）提前的亚行星点。的光变曲线折叠的范围内的行星轨道周期和相位相关的变化是定量的傅立叶方法和平均绝对偏差（MAD）的折叠数据的光度和钙II K线反转。该区域的亮度在旋转的时间尺度上变化约1 mmag。在2004年，它类似于一个深度可变的黑点，而在2005年，它在明亮和黑暗之间变化。2004年和2005年的测光结果表明，在123个行星轨道上，变区与行星轨道周期的同步误差在0.0015 d以内。2001年、2002年和2003年的Ca II K线也显示出以phi=0.8为中心的增强的K线可变性，将覆盖范围扩大到大约440个行星公转。可变区表面上恒定的旋转周期和它的快速变化使得用传统的星点来解释是不可能的。在phi=0.3和检测到的可变区域，到目前为止，提前的子行星点排除潮汐激发的补充可变性的缺乏，但结合光度和钙II K线反转的结果，使一个很好的情况下，一个活跃的区域诱导的表面上的tau Boo A的行星同伴磁。
英文摘要：
(abridged) There is considerable interest in the possible interaction between parent stars and giant planetary companions in 51 Peg-type systems. We demonstrate from MOST satellite photometry and Ca II K line emission that there has been a persistent, variable region on the surface of tau Boo A which tracked its giant planetary companion for some 440 planetary revolutions and lies ~68deg (phi=0.8) in advance of the sub-planetary point. The light curves are folded on a range of periods centered on the planetary orbital period and phase dependent variability is quantified by Fourier methods and by the mean absolute deviation (MAD) of the folded data for both the photometry and the Ca II K line reversals. The region varies in brightness on the time scale of a rotation by ~1 mmag. In 2004 it resembled a dark spot of variable depth, while in 2005 it varied between bright and dark. Over the 123 planetary orbits spanned by the photometry the variable region detected in 2004 and in 2005 are synchronised to the planetary orbital period within 0.0015 d. The Ca II K line in 2001, 2002 and 2003 also shows enhanced K-line variability centered on phi=0.8, extending coverage to some 440 planetary revolutions. The apparently constant rotation period of the variable region and its rapid variation make an explanation in terms of conventional star spots unlikely. The lack of complementary variability at phi=0.3 and the detection of the variable region so far in advance of the sub-planetary point excludes tidal excitation, but the combined photometric and Ca II K line reversal results make a good case for an active region induced magnetically on the surface of tau Boo A by its planetary companion.
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