dM4.5 e星YZ CMi上的白光巨射电望远镜
A White Light Megaflare on the dM4.5e Star YZ CMi
摘要：
在UT 2009年1月16日，我们观察到了dM4.5e恒星YZ CMi上的白光巨耀斑，这是长期光谱耀斑监测活动的一部分，以限制光学耀斑连续发射的光谱形状。在1.3小时的耀斑衰变期间，同时获得了U波段光度和3350 A-9260 A光谱观测。该事件持续了7个多小时，在耀斑峰值时，U带通量比静止状态亮近6个星等。这个耀斑的特性标志着它是有史以来在孤立的低质量恒星上观察到的最具活力和持续时间最长的白光耀斑之一。我们介绍了U波段耀斑的能量学和耀斑的连续分析。我们第一次用光谱令人信服地证明了从3350 A到4800 A的蓝色连续谱的形状可以表示为两个分量之和：一个是由Allred等人的辐射流体动力学耀斑模型预测的Balmer连续谱，另一个是由许多以前对耀斑宽带颜色和光谱分布的研究所提出的T ~ 10，000 K黑体发射分量。巴耳末连续谱和黑体发射区的面积覆盖在耀斑衰减期间变化，巴耳末连续谱发射区总是明显（~3-16倍）大。这些数据将为理解恒星耀斑中神秘的蓝色连续辐射的物理基础提供关键的约束。
英文摘要：
On UT 2009 January 16, we observed a white light megaflare on the dM4.5e star YZ CMi as part of a long-term spectroscopic flare-monitoring campaign to constrain the spectral shape of optical flare continuum emission. Simultaneous U-band photometric and 3350A-9260A spectroscopic observations were obtained during 1.3 hours of the flare decay. The event persisted for more than 7 hours and at flare peak, the U-band flux was almost 6 magnitudes brighter than in the quiescent state. The properties of this flare mark it as one of the most energetic and longest-lasting white light flares ever to be observed on an isolated low-mass star. We present the U-band flare energetics and a flare continuum analysis. For the first time, we show convincingly with spectra that the shape of the blue continuum from 3350A to 4800A can be represented as a sum of two components: a Balmer continuum as predicted by the Allred et al radiative hydrodynamic flare models and a T ~ 10,000K blackbody emission component as suggested by many previous studies of the broadband colors and spectral distributions of flares. The areal coverage of the Balmer continuum and blackbody emission regions vary during the flare decay, with the Balmer continuum emitting region always being significantly (~3-16 times) larger. These data will provide critical constraints for understanding the physics underlying the mysterious blue continuum radiation in stellar flares.
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