Flare behaviour in single and binary F and G stars – II. Cumulative flare frequency variation over stellar evolution

ABSTRACT In this study, the cumulative flare frequency (CFF) distributions of a total of 8949 flares detected from 52 F- and G-type stars, whose effective temperatures range between 5237 and 6574 K and surface gravities, $\mathrm{ log}~g$, range between 3.41 and 4.61 $\rm {cm}~{\mathrm{ s}}^{-2}$, were investigated using long cadence photometric data from the Kepler mission. Among the sample, 40 stars are single, and remaining 12 stars are members of binary systems. We compare the flare durations and equivalent durations between these two groups. In both groups, the most frequently observed flare duration is around 118 min. The distribution of equivalent durations in $log~P$ exhibits a Gaussian like profile, peaking at approximately $\mathrm{ log}~P~\approx ~1.10$ s for single stars and $\approx$1.00 s for binary stars. An analysis of flare occurrence in relation to stellar temperature reveals that cooler stars tend to exhibit a higher number of flares, regardless of their multiplicity. The CFF distributions were also examined in the context of the stellar evolutionary stage, revealing that evolved (giant) stars tend to exhibit distributions clustered at higher levels. The power-law indices ($\alpha$) of the CFF distributions range between 1.356 and 1.957 for main-sequence stars and between 1.406 and 2.01 for giants. While $\alpha$ shows only a weak correlation with effective temperature, it displays a more significant dependence on surface gravity ($\mathrm{ log}~g$), indicating a strong link to evolutionary status. These results demonstrate that flare statistics are closely associated with stellar evolution.