New Suns in the Cosmos V: Stellar rotation and multifractality in active \textit{Kepler} stars

New Suns in the Cosmos III: multifractal signature analysis

In present paper, we investigate the multifractality signatures in hourly time series extracted from CoRoT spacecraft database. Our analysis is intended to highlight the possibility that astrophysical time series can be members of a particular class of complex and dynamic processes which require several photometric variability diagnostics to characterize their structural and topological properties. To achieve this goal, we search for contributions due to nonlinear temporal correlation and effects caused by heavier tails than the Gaussian distribution, using a detrending moving average algorith…

New Suns in the Cosmos II: Differential rotation in Kepler Sun-like stars

The present study reports the discovery of Sun-like stars, namely main-sequence stars with $T_{\rm eff}$, $\log g$ and rotation periods $P_{rot}$ similar to solar values, presenting evidence of surface differential rotation. An autocorrelation of the time series was used to select stars presenting photometric signal stability from a sample of 881 stars with light curves collected by the $Kepler$ space-borne telescope, in which we have identified 17 stars with stable signals. A simple two-spot model together with a Bayesian information criterion were applied to these stars in the search for ind…

New Suns in the Cosmos IV: the multifractal nature of stellar magnetic activity in \textit{Kepler} cool stars

In the present study, we investigate the multifractal nature of a long-cadence time series observed by the \textit{Kepler} mission for a sample of 34 M dwarf stars and the Sun in its active phase. Using the Multifractal Detrending Moving Average algorithm (MFDMA), which enables the detection of multifractality in nonstationary time series, we define a set of multifractal indices based on the multifractal spectrum profile as a measure of the level of stellar magnetic activity. This set of indices is given by the ($A$,$Δα$,$C$,$H$)-quartet, where $A$, $Δα$ and $C$ are related to geometric featur…

宇宙中的新太阳？

New Suns in the Cosmos?

目前的工作报告发现了三颗恒星，我们已经确定是旋转的太阳般的恒星，根据旋转调制签名推断从光变曲线从CoRoT任务的公共档案。在我们的分析中，我们根据周期- $T_{\rm eff}$图中的旋转周期和位置执行初始选择。这表明，恒星CoRoT ID 100746852，102709980和105693572提供了潜在的良好匹配，太阳具有类似的旋转周期。为了改进我们的分析，我们应用了一种新的方法，考虑到与不同时间间隔的光度调制相关的特征的波动，以及太阳和这些“新太阳”候选者的光变曲线中存在的分形痕迹。从这个意义上说，我们计算了所谓的赫斯特指数的恒星，为14个样本的CoRoT恒星与次太阳和超级太阳旋转周期，以及太阳本身，在其活跃和安静的阶段。我们发现，赫斯特指数可以提供一个强有力的判别太阳的行为，超越了什么可以实现单独的旋转周期本身。特别是，我们发现CoRoT ID 105693572是最接近太阳自转特性的恒星，就后者对光变曲线行为的影响而言。编号为100746852和102709980的恒星的赫斯特指数明显小于太阳，尽管它们的自转周期相似。

没有证据表明太阳发电机同步性缺失

No evidence for absence of solar dynamo synchronization

本文通过分析过去千年的宇宙成因放射性核素数据，发现由$^{14}$C推断的太阳黑子数据与同步的太阳发电机模型相符，证实了金星-地球-木星系统大潮的同步作用。

太阳磁活动周期的“另一类”世纪尺度记录：来自恒星的启示

The "Other" Centuries-Long Record of Solar Magnetic Activity Cycles: Lessons From the Stars

该综述综合太阳与恒星磁活动记录，揭示类太阳发电机普遍存在，而类似蒙德极小期的磁极大极小事件极为罕见，并阐明恒星自转减慢至临界罗斯比数后磁活动减弱、周期受抑的演化图景。