Statistical properties of superflares on solar-type stars based on the Kepler 1-min cadence data

Abstract

We searched for superflares on solar-type stars using the Kepler short-cadence (1-min sampling) data in order to detect superflares with short duration. We found 187 superflares on 23 solar-type stars whose bolometric energy ranges from the order of $10^{32}$ erg to $10^{36}$ erg. Using these new data combined with the results from the data with 30-min sampling, we found the occurrence frequency ($dN/dE$) of superflares as a function of flare energy ($E$) shows the power-law distribution ($dN/dE\propto E^{-\alpha }$) with $\alpha =1.5$ for $10^{33}<E<10^{36}$ erg. The upper limit of energy released by superflares is basically comparable to a fraction of the magnetic energy stored near starspots which is estimated from the amplitude of brightness variations. We also found that the duration of superflares ($\tau$) increases with the flare energy ($E$) as $\tau \propto E^{0.39\pm 0.03}$. This can be explained if we assume the time-scale of flares is determined by the Alfv$\acute{\mathrm{e}}$n time.

6 pages, 4 figures, submitted to the proceedings of the IAU Symposium 320 "Solar and Stellar Flares and Their Effects on Planets" (eds. A. G. Kosovichev, S. L. Hawley, P. Heinzel)

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Cited by in corpus (1)

• Stellar flares detected with the Next Generation Transit Survey