Multiple and changing cycles of active stars - II. Results

By K. Ol'ah, Z. Koll'ath, T. Granzer, K. Strassmeier, Antonino Francesco Lanza, S. Jarvinen, H. Korhonen, S. Baliunas, W. Soon, S. Messina and 1 more. 2009

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Aims. We study the time variations in the cycles of 20 active stars based on decade-long photometric or spectroscopic observations. Methods. A method of time-frequency analysis, as discussed in a companion paper, is applied to the data. Results. Fifteen stars definitely show multiple cycles, but the records of the rest are too short to verify a timescale for a second cycle. The cycles typically show systematic changes. For three stars, we found two cycles in each of them that are not harmonics and vary in parallel, indicating a common physical mechanism arising from a dynamo construct. The positive relation between the rotational and cycle periods is confirmed for the inhomogeneous set of active stars. Conclusions. Stellar activity cycles are generally multiple and variable.

Subfields: Astronomy and Astrophysics, Molecular Biology

View Paper: https://www.semanticscholar.org/paper/48c24a5e86086b779473453831ceabceb9939761

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Citations in the corpus

MAGNETIC WREATHS AND CYCLES IN CONVECTIVE DYNAMOS (2012, background): “There have been a number of attempts to monitor the magnetic activity cycles of other stars using solar-calibrated proxies for magnetic activity (e.g., Baliunas et al. 1995; Hempelmann et al. 1996; Oláh et al. 2009).”
MAGNETIC CYCLES IN A CONVECTIVE DYNAMO SIMULATION OF A YOUNG SOLAR-TYPE STAR (2011, methodology): “Longer-term but more sporadic photometric measurements are available for a few dozen stars and these, along with the Mount Wilson data, show evidence for multiple periodicities and possible variations in the apparent starspot cycle periods over the course of multiple decades (Oláh et al. 2009).”