Prediction of short stellar activity cycles using derived and established empirical relations between activity and rotation periods

Abstract

In our previous work, we investigated the occurrence rate of super-flares on various types of stars and their statistical properties, with a particular focus on G-type dwarfs, using entire Kepler data. The said study also considered how the statistics change with stellar rotation period, which in turn, had to be determined. Using such new data, as a by-product, we found 138 Kepler IDs of F and G types main sequence stars with rotation periods less than a day ($P_{\rm rot}<1$ d). On one hand, previous studies have revealed short activity cycles in F-type and G-type stars and the question investigated was whether or not short-term activity cycles are a common phenomenon in these stars. On the other hand, extensive studies exist which establish empirical connection between a star's activity cycle and rotation periods. In this study, we compile all available Kepler data with $P_{\rm rot}<1$ d, derive and use, established empirical relation between $P_{\rm cyc}$ and $P_{\rm rot}$ with the aim to provide predictions for very short $5.09\leq P_{\rm cyc}\leq 38.46$ d cases in a tabular form. We propose an observation to measure $P_{\rm cyc}$ using monitoring program of stellar activity (e.g. activity-related chromospheric emission S-index) or similar means for the Kepler IDs found in this study in order put to test the derived here empirical relations between $P_{\rm cyc}$ and $P_{\rm rot}$. We also propose an alternative method for measuring very short $P_{\rm cyc}$, using flare-detection algorithms applied to future space mission data.