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arXiv · 2310.16974

Multicomponent Activity Cycles using Hilbert-Huang Analysis

E. N. Velloso·F. Anthony·J. D. do Nascimento Jr·L. F. Q. Silveira·J. Hall·S. H. Saar
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Abstract

The temporal analysis of stellar activity evolution is usually dominated by a complex trade-off between model complexity and interpretability, often by neglecting the non-stationary nature of the process. Recent studies appear to indicate that the presence of multiple coexisting cycles in a single star is more common than previously thought. The correct identification of physically meaningful cyclic components in spectroscopic time series is therefore a crucial task, which cannot overlook local behaviors. Here we propose a decomposition technique which adaptively recovers amplitude- and frequency-varying components. We present our results for the solar activity as measured both by the sunspot number and the $K$-line emission index, and we consistently recover the Schwabe and Gleissberg cycles as well as the Gnevyshev-Ohl pattern probably related to the Hale cycle. We also recover the known 8-year cycle for 61 Cygni A, in addition to evidence of a three-cycles long pattern reminiscent of the Gnevyshev-Ohl rule. This is particularly interesting as we cannot discard the possibility of a relationship between the measured field polarity reversals and this Hale-like periodicity.

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E. N. Velloso, F. Anthony, J. D. do Nascimento Jr, L. F. Q. Silveira, J. Hall, S. H. Saar. 2023-10-25. Multicomponent Activity Cycles using Hilbert-Huang Analysis. https://doi.org/10.3847/2041-8213/acb8b4

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