Main-sequence star super-flares based on entire Kepler data

TL;DR

This study analyzes super-flares on main-sequence stars across all spectral types using Kepler data, revealing statistical properties, occurrence rates, and differences in flare distributions among star types.

Contribution

It provides a comprehensive statistical analysis of super-flares across all main-sequence star types using the entire Kepler dataset, including new insights into flare frequency distributions.

Findings

Super-flares on G-type stars occur roughly once every 4360 years at 10^{35} erg.

Power-law distribution with index ~2.0-2.1 for F to M stars, but ~1.3 for A stars.

Increase in flare incidence from F to M stars, decrease from A to F stars.

Abstract

We wrote and used an automated flare detection Python script to search for super-flares on main-sequence stars of types A, F, G, K, and M in Kepler's long-cadence data from Q0 to Q17. We studied the statistical properties of the occurrence rate of super-flares. For the G-type data set, we compared our results with the previous results of Okamoto et al. 2021 by splitting the data set into four rotational bands. We found similar power law indices for the flare frequency distribution. Hence, we show that inclusion of high-pass filter, sample biases, gyrochronology and completeness of flare detection is of no significance, as our results are similar to Okamoto et al. 2021. We estimated that a super-flare on G-type dwarfs of energy of $10^{35}$ erg occurs on a star once every 4360 years. We found 4637 super-flares on 1896 G-type dwarfs. Moreover, we found 321, 1125, 4538 and 5445 super-flares on 136, 522, 770 and 312 dwarfs of types A, F, K and M, respectively. We found that the occurrence rate ($dN/dE$) of super-flares versus flare energy, $E$, shows a power-law distribution with $dN/dE \propto E^{-\alpha}$, where $\alpha \simeq$ 2.0 to 2.1 for the spectral types from F-type to M-type stars. In contrast, the obtained $\alpha \simeq$ 1.3 for A-type stars suggests that the flare conditions differ from the rest spectral-type stars. We note an increase in flare incidence rate in F-type to M-type stars and a decrease in A-type to F-type stars.