用Seimei望远镜、SCAT、NICER和OISTER对活动M矮星AD Leonis上恒星耀斑的光学和X射线观测
Optical and X-ray observations of stellar flares on an active M dwarf AD Leonis with Seimei Telescope, SCAT, NICER and OISTER
摘要：
本文报道了用晴明望远镜（6150- 7930千电子伏特）、中央大学光谱天文望远镜（3700- 7500千电子伏特）、中子星内部成分探测器（0.2- 12.0千电子伏特）和光学与红外协同望远镜（OISTER）对M矮星狮子座AD的多波长监测观测。总共探测到12个耀斑，其中包括10个H $α$，4个X射线和4个光学连续谱耀斑，其中一个是总能量为$\sim$ 2.0 $\times$ 10 $^{33}$ erg的超级耀斑。我们发现：（1）在超耀斑期间，H $α$发射谱线的1/8峰全宽从低分辨率谱的8 μ m急剧增加到14 μ m（2）某些弱H $\sim$/X射线耀斑不伴有白光发射，（3）非耀斑发射在同相位的X射线和H $α$强度中显示出明显的转动调制。为了了解这些观测特征，一维流体动力学耀斑模拟使用RADYN程序。模拟结果表明，在硬电子束和高能非热电子束作用下，模拟的H PDMATHAMM谱线轮廓与超耀斑的初始相线轮廓一致，而在软电子束和低能电子束作用下，模拟的H PDMATHAMM谱线轮廓与超耀斑的衰变相线轮廓一致，表明注入低层大气的能量通量发生了变化。另外，我们还发现光学连续谱与H $α$强度之间存在非线性关系，这可能是产生非白光耀斑的原因之一。耀斑的能量收支在观测和模型上表现出多样性，需要更多的恒星耀斑观测来约束恒星耀斑中各种发射线现象的发生。
英文摘要：
We report multi-wavelength monitoring observations of an M-dwarf flare star AD Leonis with Seimei Telescope (6150--7930 Å), SCAT (Spectroscopic Chuo-university Astronomical Telescope; 3700--7500 Å), NICER (Neutron Star Interior Composition Explorer; 0.2--12.0 keV), and collaborations of OISTER (Optical and Infrared Synergetic Telescopes for Education and Research) program. Twelve flares are detected in total which include ten H$α$, four X-ray, and four optical-continuum flares; one of them is a superflare with the total energy of $\sim$ 2.0$\times$10$^{33}$ erg. We found that (1) during the superflare, the H$α$ emission line full width at 1/8 maximum dramatically increases to 14 Å from 8 Å in the low-resolution spectra (R$\sim$ 2000) accompanied with the large white-light flares, (2) some weak H$α$/X-ray flares are not accompanied with white-light emissions, and (3) the non-flaring emissions show clear rotational modulations in X-ray and H$α$ intensity in the same phase. To understand these observational features, one-dimensional hydrodynamic flare simulations are performed by using the RADYN code. As a result of simulations, we found the simulated H$α$ line profiles with hard and high-energy non-thermal electron beams are consistent with that of the initial phase line profiles of the superflares, while those with more soft- and/or weak-energy beam are consistent with those in decay phases, indicating the changes in the energy fluxes injected to the lower atmosphere. Also, we found that the relation between optical continuum and H$α$ intensity is nonlinear, which can be one cause of the non-white-light flares. The flare energy budget exhibits diversity in the observations and models, and more observations of stellar flares are necessary for constraining the occurrence of various emission line phenomena in stellar flares.
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