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Title: Statistical properties of superflares on solar-type stars based on 1-min cadence data
Authors: Maehara, Hiroyuki
Shibayama, Takuya
Notsu, Yuta
Notsu, Shota
Honda, Satoshi
Nogami, Daisaku
Shibata, Kazunari
Author's alias: 野上, 大作
柴田, 一成
Keywords: Superflares
Solar flares
Stellar flares
Solar-type stars
Extreme space weather events
Issue Date: 29-Apr-2015
Publisher: SpringerOpen
Journal title: Earth, Planets and Space
Volume: 67
Thesis number: 59
Abstract: We searched for superflares on solar-type stars using Kepler data with 1-min sampling in order to detect superflares with a short duration. We found 187 superflares on 23 solar-type stars whose bolometric energy ranges from the order of 10<sup>32</sup> to 10<sup>36</sup> erg. Some superflares show multiple peaks with the peak separation of the order of 100 to 1, 000 s 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 that the occurrence frequency (dN/dE) of superflares as a function of flare energy (E) shows the power-law distribution (dN/dE∞E <sup>-α</sup> ) with α∼-1.5 for 10<sup>33</sup><E<10<sup>36</sup> erg which is consistent with the previous results. The average occurrence rate of superflares with the energy of 10<sup>33</sup> erg which is equivalent to X100 solar flares is about once in 500 to 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∞E <sup>0.39 ± 0.03</sup>. This can be explained if we assume the time scale of flares is determined by the Alfvén time.
Rights: © 2015 Maehara et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.
DOI(Published Version): 10.1186/s40623-015-0217-z
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