Empirically revealed properties of Rieger-type cycles of stellar activity

Context. The Rieger cycles were discovered in the Sun as a specific 154-day periodicity of flare occurrence; they strongly influence terrestrial space weather. This phenomenon is far from being understood. Various proposed mechanisms for this need further verification stars with stellar parameters different those Sun. Aims. In work, we study Rieger-type cycle (RTC) periods P RTC activity surveyed photometric data Kepler telescope. Methods. processing 1726 light curves reveals statistics values main-sequence effective temperatures T eff and rotation . uses an index squared amplitude first rotational harmonic A 1 2 curve variability. Results. obtained information on considered confirms phenomenological analogy between RTCs solar cycles. Two types found: (1) independent rotation, which are typical ≲ 5500 K, (2) proportional to period , take place ≳ 6300 K. These two can be driven by Kelvin Rossby waves, respectively. wave-driven show relation location tachocline at shallow depths hot stars. theoretical predictions connection tachocline. At same time, do not connection. Apparently, both wave drivers coexist, resulting joint modulation magnetic flux tubes emergence corresponding behavior Conclusions. signatures their relations call revision elaboration theory RTCs.