However, the energy of the largest flares observed in a given period bin does not show any clear correlation with the rotation Rotation period, and that the flare frequency increases as the rotation period decreases. Furthermore, our analyses indicate that the occurrence frequency of superflares depends on the The bolometric energy released by flares is consistent with the magnetic energy stored around such large starspots. This interpretation is also supported by our spectroscopic studies with Subaru/HDS (Notsu+2015a&2015b, PASJ). Using these data, we found that the occurrenceįrequency (dN/dE) of superflares is expressed as a power-law function of flare energy (E) with the index of -1.5 for 10^33 the superflare stars show quasi-periodic light variations with the amplitude of a few percent, which can be explained by the rotation of the star with large starspots (Notsu+2013, ApJ). The bolometric energy of detected superflares ranges from the order of 10^32 erg to 10^36 erg. (5) We chose the peak from the power spectrum whose amplitude had the highest ratio.
(Maehara+2012 Nature Maehara+2015 EPS Shibayama+2013 ApJS). Yuta Notsu1, Takuya Shibayama1, Hiroyuki Maehara2,3, Shota Notsu1. We found more than 1500 superflares on 279 stars from 30-min cadence data (Q0-6) and 187 superflares on 23 stars from 1-min cadence data (Q0-17) Using the Kepler 30-min (long) and 1-min (short) cadence data.
We searched superflares on solar-type stars (G-type main sequence stars) As a result, Sun-like stars can cause superflares with energies up to about 5×10 34 erg once every ∼5000 years, and this strongly supports the possiblity of superflares on the Sun.Superflares are flares that release total energy 10∼10^4 times greater than that of the biggest solar flares with energy of ∼10^32 erg. Frequency of superflares decreases as the stellar age increases, and flare frequency as a function of flare energy shows power-law distributions (dN/dE ~ E α with α ≳ -2). These can be consistent with the result that the starspot coverage decrease as the rotation period increases. As a result, the upper limit of the flare energy decreases as the rotation period (stellar age) increases in solar-type stars, while flare energy can be explained by the magnetic energy stored around starspots. (2019), which enabled us to discuss more well-established view on statistical properties of superflares on Sun-like stars. As a result, the number of superflares on Sun-like stars in this study greatly increased by ∼12 times compared with Notsu et al. We also took into account the effect of sample biases on the frequency of superflares, by considering gyrochronology and flare detection completeness. We updated the flare detection method by using high-pass filter to remove rotational variations caused by starspots. in prep), we searched for superflares using all the Kepler 4-year primary mission data covering ∼1500 days, adding the targets newly identified as solar-type stars. Then in our latest study (Okamoto, Notsu, Maehara et al. As a result, the number of Sun-like (slowly-rotating solar-type) superflare stars significantly decreased. (2019 ApJ) conducted precise measurements of the stellar parameters and binarity check on the basis of spectroscopic observations and the Gaia-DR2 data. Recently, many superflares on solar-type stars were found in the initial 500 days data obtained by the Kepler spacecraft (Maehara et al. It had been thought that superflares cannot occur on slowly-rotating solar-type (G-type main-sequence) stars like the Sun. Solar flares are energetic explosions in the solar atmosphere, and superflares are the flares having the energy 10–10 6 times larger than that of the largest solar flare.
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