光变曲线自相关函数与激活区寿命的关系
On the relation between active-region lifetimes and the autocorrelation function of light curves
摘要：
恒星光变曲线的旋转调制，由于暗点包含的信息点的属性，因此，对磁活动。特别是，光变曲线的自相关函数（ACF）的衰减被认为是链接到点/有源区的寿命，考虑到一些相干的信号，预计在整个寿命。文献中采用指数衰减来描述ACF。在这里，我们调查ACF和有源区寿命之间的关系。为了这个目的，我们产生人工光变曲线的旋转斑点星不同的观察，恒星，和现场的属性。我们发现，线性衰减和各自的时间尺度更好地代表ACF比指数衰减。因此，我们采用线性衰减。从ACF推断出的光斑/活动区时间尺度受到光变曲线的观测长度的强烈限制。对于1年的光变曲线，我们的结果是一致的，推断和输入时标之间没有相关性。ACF衰减也受到差分旋转和光斑演化的显著影响：强差分旋转和快速光斑演化导致更严重的有源区寿命低估。然而，在这两种情况下，观察到的时间尺度仍然与输入寿命相关。因此，我们的分析表明，ACF衰变可以用来获得一个较低的限制的活性区寿命相对较长的观察。然而，应采用避免或标记具有快速活性区域演变或显示与差分旋转相关的稳定跳动模式的目标的策略。
英文摘要：
Rotational modulation of stellar light curves due to dark spots encloses information on spot properties and, thus, on magnetic activity. In particular, the decay of the autocorrelation function (ACF) of light curves is presumed to be linked to spot/active-region lifetimes, given that some coherence of the signal is expected throughout their lifetime. In the literature, an exponential decay has been adopted to describe the ACF. Here, we investigate the relation between the ACF and the active-region lifetimes. For this purpose, we produce artificial light curves of rotating spotted stars with different observation, stellar, and spot properties. We find that a linear decay and respective timescale better represent the ACF than the exponential decay. We therefore adopt a linear decay. The spot/active-region timescale inferred from the ACF is strongly restricted by the observation length of the light curves. For 1-year light curves our results are consistent with no correlation between the inferred and the input timescales. The ACF decay is also significantly affected by differential rotation and spot evolution: strong differential rotation and fast spot evolution contribute to a more severe underestimation of the active-region lifetimes. Nevertheless, in both circumstances the observed timescale is still correlated with the input lifetimes. Therefore, our analysis suggests that the ACF decay can be used to obtain a lower limit of the active-region lifetimes for relatively long-term observations. However, strategies to avoid or flag targets with fast active-region evolution or displaying stable beating patterns associated with differential rotation should be employed.
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