تقرير
New Suns in the Cosmos IV: the multifractal nature of stellar magnetic activity in \textit{Kepler} cool stars
| العنوان: | New Suns in the Cosmos IV: the multifractal nature of stellar magnetic activity in \textit{Kepler} cool stars |
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| المؤلفون: | de Freitas, D. B., Nepomuceno, M. M. F., de Souza, M. Gomes, Leão, I. C., Chagas, M. L. Das, Costa, A. D., Martins, B. L. Canto, De Medeiros, J. R. |
| سنة النشر: | 2017 |
| المجموعة: | Astrophysics |
| مصطلحات موضوعية: | Astrophysics - Solar and Stellar Astrophysics |
| الوصف: | 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 ($A$,$\Delta \alpha$,$C$,$H$)-quartet, where $A$, $\Delta \alpha$ and $C$ are related to geometric features from the multifractal spectrum and the global Hurst exponent $H$ describes the global structure and memorability of time series dynamics. As a test, we measure these indices and compare them with a magnetic index defined as $S_{ph}$ and verify the degree of correlation among them. First, we apply the Poincar\'e plot method and find a strong correlation between the $\left\langle S_{ph}\right\rangle$ index and one of the descriptors that emerges from this method. As a result, we find that this index is strongly correlated with long-term features of the signal. From the multifractal perspective, the $\left\langle S_{ph}\right\rangle$ index is also strongly linked to the geometric properties of the multifractal spectrum except for the $H$ index. Furthermore, our results emphasize that the rotation period of stars is scaled by the $H$ index, which is consistent with Skumanich's relationship. Finally, our approach suggests that the $H$ index may be related to the evolution of stellar angular momentum and a star's magnetic properties. Comment: 8 figures and 3 tables (Accepted to ApJ) |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.3847/1538-4357/aa78aa |
| URL الوصول: | http://arxiv.org/abs/1706.02935 |
| رقم الأكسشن: | edsarx.1706.02935 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.3847/1538-4357/aa78aa |
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