Discovery of short-term activity cycles in F-type stars

Previous studies have revealed a 120 day activity cycle in the F-type star τ Boo, which represents the shortest activity cycle discovered until now. The question arises as to whether or not short-term activity cycles are a common phenomenon in F-type stars. To address this question, we analyse S-ind...

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Bibliographic Details
Published in:Astronomy and astrophysics (Berlin) 2019, Vol.621, p.A136
Main Authors: Mittag, M., Schmitt, J. H. M. M., Hempelmann, A., Schröder, K.-P.
Format: Article
Language:English
Subjects:
Amplitudes
Main sequence stars
Periodic variations
Short term
Stars
stars: activity
stars: atmospheres
stars: chromospheres
stars: late-type
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Summary:Previous studies have revealed a 120 day activity cycle in the F-type star τ Boo, which represents the shortest activity cycle discovered until now. The question arises as to whether or not short-term activity cycles are a common phenomenon in F-type stars. To address this question, we analyse S-index time series of F-type stars taken with the TIGRE telescope to search for periodic variations with a maximal length of 2 years using the generalised Lomb-Scargle periodogram method. In our sample, we find four F-type stars showing periodic variations shorter than one year. However, the amplitude of these variations in our sample of F-star type stars appears to be smaller than that of solar-type stars with well-developed cyclic activity, and apparently represents only a part of the total activity. We conclude that among F-stars, the time-behaviour of activity differs from that of the Sun and cooler main sequence stars, as short-term cyclic variations with shallow amplitude of the cycle seem to prevail, rather than cycles with 10+ years periods and a larger cycle amplitude.
ISSN:0004-6361
1432-0746
DOI:10.1051/0004-6361/201834319