耀斑等待时间：恒星磁活动的新型代理指标
Flare waiting time as a novel proxy of stellar magnetic activity
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中文总结 AI 辅助
本研究以开普勒卫星观测的耀斑M型矮星为样本，提出耀斑等待时间中位数作为新型恒星磁活动代理指标，首次明确其与恒星自转周期的关系，发现该指标表现出更显著的超饱和效应，将助力恒星磁活动研究。
中文摘要 AI 辅助
长期以来，恒星耀斑一直作为恒星磁活动的示踪物。耀斑等待时间被定义为两次连续耀斑之间的间隔，为探测恒星大气中能量存储与释放的潜在机制提供了有价值的诊断工具。本研究利用开普勒（Kepler）卫星观测到的耀斑M型矮星，建立了一个简单却有效的活动代理指标，即耀斑等待时间中位数（$t_{\rm{w, med}}$）。结果表明，$t_{\rm{w, med}}$可像耀斑发生率一样追踪长期活动水平，但不同等待时间分位数对应的$t_{\rm{w, med}}$可能比耀斑发生率蕴含更丰富的物理信息。此外，本研究首次构建了$t_{\rm{w, med}}$与恒星自转周期之间的清晰关系，该关系与经典的活动-自转关系极为相似。更引人注目的是，与其他活动代理指标相比，该关系表现出更显著的超饱和效应（即低于临界自转周期时，$t_{\rm{w, med}}$开始增加而非保持恒定）。填充因子-自转周期关系支持活动区向极区迁移是超饱和的成因，而非日冕剥离。随着凌星系外行星巡天卫星（TESS）等任务探测到的恒星耀斑数量大幅增加，以及即将到来的地球2.0卫星的发射，$t_{\rm{w, med}}$将成为探测恒星磁活动及潜在物理机制的有力工具。
英文摘要
Stellar flares have long served as stellar magnetic activity tracers. The flare waiting time, defined as the interval between two consecutive flares, provides a valuable diagnostic for probing underlying mechanisms of energy storage and release in stellar atmospheres. In this work, utilizing flaring M dwarfs observed by the Kepler satellite, we establish a simple yet effective activity proxy, i.e., median flare waiting time ($t_{\rm{w, med}}$). Our results show that the $t_{\rm{w, med}}$ can trace long-term activity levels similar to the flare rate. However, $t_{\rm{w, med}}$ corresponding to different waiting time percentiles may encode richer physical insights than flare rate. In addition, for the first time we construct a clear relation between $t_{\rm{w, med}}$ and stellar rotation period, which is quite similar to the canonical activity--rotation relation. More intriguingly, this relation exhibits a more notable supersaturation effect (i.e., below a critical rotation period, $t_{\rm{w, med}}$ begins to increase instead of keeping constant) compared to other activity proxies. The filling factor--rotation period relation favors poleward migration of active regions as the explanation for supersaturation, rather than coronal stripping. With the dramatic increase in stellar flares detected by missions like TESS and the upcoming Earth 2.0 satellite, $t_{\rm{w, med}}$ will become a powerful diagnostic for probing stellar magnetic activity and underlying physics.
