SUPERFLARE OCCURRENCE AND ENERGIES ON G-, K-, AND M-TYPE DWARFS
SUPERFLARE OCCURRENCE AND ENERGIES ON G-, K-, AND M-TYPE DWARFS
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DOI：
10.1088/0004-637x/792/1/67
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发表时间：
2014-05
期刊：
影响因子：
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通讯作者：
S. Candelaresi;Andrew Hillier;Hiroyuki Maehara;Axel Brandenburg;Kazunari Shibata
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作者：
S. Candelaresi;Andrew Hillier;Hiroyuki Maehara;Axel Brandenburg;Kazunari Shibata
开普勒从G-，K-和M-型恒星的数据被用来研究导致能量超过1034 erg的超级耀斑的条件。在包含的117，661颗恒星中，有380颗显示出超级耀斑，总共有1690次这样的事件。我们研究是否参数，如有效温度或旋转速率，有任何影响的超耀斑发生率或能量。随着有效温度的增加，我们观察到的超耀斑率的下降，这是类似于以前的研究结果，发电机活动随着有效温度的增加而减少。对于缓慢旋转的恒星，我们发现一个二次增加的平均出现率与旋转速率的临界点，之后的速率线性下降。受标准发电机理论的启发，我们研究了相对星斑覆盖率的行为，近似为相对亮度变化。对于旋转速度更快的恒星，恒星比例的增加显示出更高的光斑覆盖率，这导致更高的超级耀斑率。利用湍流发电机研究了欧姆耗散作为耀斑能量的代表对差分旋转或剪切速率的依赖关系。作为发电机数的函数的耗散能的统计结果是类似的观测到的耀斑的统计作为反Rossby数的函数，并显示出类似的强烈波动。这支持了超级耀斑很可能存在于太阳型G星的想法。
Kepler data from G-, K-, and M-type stars are used to study conditions that lead to superflares with energies above 1034 erg. From the 117,661 stars included, 380 show superflares with a total of 1690 such events. We study whether parameters, like effective temperature or rotation rate, have any effect on the superflare occurrence rate or energy. With increasing effective temperature we observe a decrease in the superflare rate, which is analogous to the previous findings of a decrease in dynamo activity with increasing effective temperature. For slowly rotating stars, we find a quadratic increase of the mean occurrence rate with the rotation rate up to a critical point, after which the rate decreases linearly. Motivated by standard dynamo theory, we study the behavior of the relative starspot coverage, approximated as the relative brightness variation. For faster rotating stars, an increased fraction of stars shows higher spot coverage, which leads to higher superflare rates. A turbulent dynamo is used to study the dependence of the Ohmic dissipation as a proxy of the flare energy on the differential rotation or shear rate. The resulting statistics of the dissipation energy as a function of dynamo number is similar to the observed flare statistics as a function of the inverse Rossby number and shows similarly strong fluctuations. This supports the idea that superflares might well be possible for solar-type G stars.