Searching for evidence of stellar cycles by using variations in flares rate

Abstract

In this work, evidence of stellar cycles is searched by analyzing variations in the rate of stellar flares. The focus is on two main sequence M-type stars plus an additional G-type target, all of them observed for 12-13 years by the Kepler and TESS missions. Each star’s data was detrended, and a flare detection method was applied. Then, in order to assess the existence of stellar cycles their cumulative Flare Frequency Distribution (FFD) was computed, as well as their fractional luminosity evolution. The typical distinct regions of a cumulative FFD, including the FFD’s turnoff point, were identified in the Kepler plots for all targets. On the TESS plots, such morphology was generally less apparent. The evolution of the fractional luminosity exhibited a decreasing trend of 0.4-0.5 decimal exponents throughout the entire timescale in those stars that showed evidence of activity cycles. The validity of such evidence claims is also discussed