SUPERFLARES ON SOLAR-TYPE STARS OBSERVED WITH KEPLER. I. STATISTICAL PROPERTIES OF SUPERFLARES

By Takuya Shibayama, Hiroyuki Maehara, S. Notsu, Y. Notsu, T. Nagao, Satoshi Honda, T. Ishii, D. Nogami, Kazunari Shibata. 2013

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By extending our previous study by Maehara et al., we searched for superflares on G-type dwarfs (solar-type stars) using Kepler data for a longer period (500 days) than that (120 days) in our previous study. As a result, we found 1547 superflares on 279 G-type dwarfs, which is much more than the previous 365 superflares on 148 stars. Using these new data, we studied the statistical properties of the occurrence rate of superflares, and confirmed the previous results, i.e., the occurrence rate (dN/dE) of superflares versus flare energy (E) shows a power-law distribution with dN/dE∝E−α, where α ∼ 2. It is interesting that this distribution is roughly similar to that for solar flares. In the case of the Sun-like stars (with surface temperature 5600–6000 K and slowly rotating with a period longer than 10 days), the occurrence rate of superflares with an energy of 1034–1035 erg is once in 800–5000 yr. We also studied long-term (500 days) stellar brightness variation of these superflare stars and found that in some G-type dwarfs the occurrence rate of superflares was extremely high, ∼57 superflares in 500 days (i.e., once in 10 days). In the case of Sun-like stars, the most active stars show a frequency of one superflare (with 1034 erg) in 100 days. There is evidence that these superflare stars have extremely large starspots with a size about 10 times larger than that of the largest sunspot. We argue that the physical origin of the extremely high occurrence rate of superflares in these stars may be attributed to the existence of extremely large starspots.

Subfields: Astronomy and Astrophysics, Education, Instrumentation

View Paper: https://www.semanticscholar.org/paper/8ac221f9c26fe9068359b8e244b241d79f647e55

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Citations in the corpus

Flare stars across the H–R diagram (2015, background): “…photometric observations from space from the Kepler satellite not only provided the opportunity for the discovery of superflares on cool stars (Maehara et al., 2012; Shibayama et al., 2013), but also lead to the discovery of superflares on stars hotter than 7500 K (the A stars; Balona, 2012).”
Statistical properties of superflares on solar-type stars based on 1-min cadence data (2015, methodology): “…National Astronomical Observatory of Japan, 3037-5 Honjo, Kamogata, Asakuchi, Okayama 719-0232, Japan Full list of author information is available at the end of the article stars) have been discovered by the Kepler space telescope (Maehara et al. 2012; Shibayama et al. 2013; Wu et al. 2015).”
25 Years of Self-Organized Criticality: Solar and Astrophysics (2014, methodology): “…Arzner and Güdel (2004), Arzner et al. (2007), Stelzer et al. (2007), Maehara et al. 2012; Shibayama et al. (2013); 24) Maehara et al. (2012); Shibayama et al. (2013); 25) Argyle and Gower (1972), Lundgren et al. (1995); 26) Cognard et al. (1996); 27) Gogus et al. (1999, 2000); 28) Negoro…”
THE KEPLER CATALOG OF STELLAR FLARES (2016, background): “Shibayama et al. (2013) accomplish this by assum- ing blackbody radiation from both the star and flare, as well as a fixed flare temperature of 10, 000 K.”
The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present (2016, background): “The current Sun, as well as average Sun-like stars observed by Kepler, and Proxima, are flaring at roughly the same rate, which is a factor of ∼10 higher than solar minimum (Shibayama et al. 2013).”
Stellar Flares from the First TESS Data Release: Exploring a New Sample of M Dwarfs (2019, methodology): “Measuring the flare energy We calculate the flare energy from the stellar luminosity and the best fitting flare profile, following Shibayama et al. (2013).”
Quasi-periodic Pulsations in Solar and Stellar Flares: An Overview of Recent Results (Invited Review) (2016, methodology): “This was recently made prominent by the use of Kepler data (Walkowicz et al., 2011; Maehara et al., 2012; Balona, 2012; Shibayama et al., 2013; Candelaresi et al., 2014).”