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标题：Discovery of short-term activity cycles in F-type stars
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作者：M. Mittag ; J. H. M. M. Schmitt ; A. Hempelmann 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2019
卷号：621
DOI：10.1051/0004-6361/201834319
语种：English
出版社：EDP Sciences
摘要：Previous studies have revealed a 120 day activity cycle in the F-type starτBoo, 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 analyseS-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.
关键词：enstars: activitystars: atmospheresstars: chromospheresstars: late-type