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

Hiroyuki Maehara; Takuya Shibayama; Yuta Notsu; Shota Notsu; Satoshi Honda; Daisaku Nogami; Kazunari Shibata

doi:10.1186/s40623-015-0217-z

paper

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

arXiv:1504.00074 · doi:10.1186/s40623-015-0217-z

Abstract

We searched for superflares on solar-type stars using Kepler data with 1 min sampling 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 $1 0^{32}$ erg to $1 0^{36}$ erg. Some superflares show multiple peaks with the peak separation of the order of $100$ - $1000$ seconds which is comparable to the periods of quasi-periodic pulsations in solar and stellar flares. Using these new data combined with the results from the data with 30 min sampling, we found the occurrence frequency ( $d N / d E$ ) of superflares as a function of flare energy ( $E$ ) shows the power-law distribution ( $d N / d E \propto E^{- α}$ ) with $α \sim - 1.5$ for $1 0^{33} < E < 1 0^{36}$ erg which is consistent with the previous results. The average occurrence rate of superflares with the energy of $1 0^{33}$ erg which is equivalent to X100 solar flares is about once in 500-600 years. 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 photometry. We also found that the duration of superflares ( $τ$ ) increases with the flare energy ( $E$ ) as $τ \propto E^{0.39 \pm 0.03}$ . This can be explained if we assume the time-scale of flares is determined by the Alfv $e ˊ$ n time.

arXiv commentAccepted for for publication in Earth, Planets and Space

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

Abstract

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