Superflares may provide the dominant source of biologically relevant UV radiation to rocky habitable zone M-dwarf planets (M-Earths), altering planetary atmospheres and conditions for surface life. The combined line and continuum flare emission has usually been approximated by a 9000 K blackbody. If superflares are hotter, then the UV emission may be 10X higher than predicted from the optical. However, it is unknown for how long M-dwarf superflares reach temperatures above 9000 K. Only a handful of M-dwarf superflares have been recorded with multi-wavelength high-cadence observations. We double the total number of events in the literature using simultaneous Evryscope and TESS observations to provide the first systematic exploration of the temperature evolution of M-dwarf superflares. We also increase the number of superflaring M-dwarfs with published time-resolved blackbody evolution by ~10X. We measure temperatures at 2 min cadence for 42 superflares from 27 K5-M5 dwarfs. We find superflare peak temperatures (defined as the mean of temperatures corresponding to flare FWHM) increase with flare energy and impulse. We find the amount of time flares emit at temperatures above 14,000 K depends on energy. We discover 43% of the flares emit above 14,000 K, 23% emit above 20,000 K and 5% emit above 30,000 K. The largest and hottest flare briefly reached 42,000 K. Some do not reach 14,000 K. During superflares, we estimate M-Earths orbiting <200 Myr stars typically receive a top-of-atmosphere UV-C flux of ~120 W m^-2 and up to 10^3 W m^-2, 100-1000X the time-averaged XUV flux from Proxima Cen.

中文翻译：

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EvryFlare。三、Evryscope 和 TESS 同时观测到的数十个超级耀斑的温度演变和宜居性影响

超级耀斑可能为岩石宜居带 M 矮行星 (M-Earths) 提供生物相关紫外线辐射的主要来源，改变行星大气和地表生命条件。组合的线和连续谱耀斑发射通常由 9000 K 黑体近似。如果超级耀斑更热，那么紫外线辐射可能比光学预测的高 10 倍。然而，M 矮星超级耀斑达到 9000 K 以上温度的时间尚不清楚。只有少数 M 矮星超级耀斑被多波长高节奏观测记录到。我们使用同步 Evryscope 和 TESS 观测将文献中的事件总数增加了一倍，以提供对 M 矮星超级耀斑温度演变的首次系统探索。我们还将发布时间分辨黑体演化的超耀斑 M 矮星的数量增加了约 10 倍。我们以 2 分钟的节奏测量来自 27 个 K5-M5 矮星的 42 个超级耀斑的温度。我们发现超级耀斑峰值温度（定义为与耀斑 FWHM 对应的温度平均值）随着耀斑能量和脉冲而增加。我们发现耀斑在高于 14,000 K 的温度下发出的时间取决于能量。我们发现 43% 的耀斑在 14,000 K 以上发射，23% 在 20,000 K 以上发射，5% 在 30,000 K 以上发射。最大和最热的耀斑短暂达到 42,000 K。有些没有达到 14,000 K。在超级耀斑期间，我们估计 M-环绕 <200 Myr 恒星运行的地球通常会收到约 120 W m^-2 和高达 10^3 W m^-2 的大气顶 UV-C 通量，是来自 Proxima Cen 的时间平均 XUV 通量的 100-1000 倍.