Large X-ray flares on stars detected with MAXI/GSC: A universal correlation between the duration of a flare and its X-ray luminosity
Large X-ray flares on stars detected with MAXI/GSC: A universal correlation between the duration of a flare and its X-ray luminosity
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使用 MAXI/GSC 检测到的恒星上的大型 X 射线耀斑：耀斑持续时间与其 X 射线光度之间的普遍相关性
DOI：
10.1093/pasj/psw081
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发表时间：
2016
影响因子：
2.3
通讯作者：
et al.
中科院分区：
文献类型：
--
作者：
Y. Tsuboi;K. Yamazaki;Y. Sugawara;A. Kawagoe;S. Kaneto;R. Iizuka;T. Matsumura;S. Nakahira;M. Higa;M. Matsuoka;M. Sugizaki;Y. Ueda;N. Kawai;M. Morii;M. Serino;T. Mihara;H. Tomida;S. Ueno;H. Negoro;N. Isobe;H. Tsunemi;et al.
在我们使用全天 X 射线图像监视器 (MAXI) 的气体比例计数器 (GSC) 进行全天 X 射线监测的头两年中，检测到了来自 13 个活跃恒星（8 个 RS CVn 系统、1 个大陵五系统、3 个 dMe 星和一个年轻恒星物体）的 23 个巨大耀斑。所有这些 MAXI/GSC 耀斑的观测参数均处于恒星耀斑的上限，在 2-20 keV 波段光度为 1031-34erg s−1，发射量度为 1054-57cm−3，折叠时间为 1 小时到 1.5 d，耀斑期间释放的总辐射能为1034–39erg。值得注意的是，在 II Peg 上的一个耀斑中检测到了 2-20 keV 波段的 X 射线峰值光度 erg s−1，这是有史以来观测到的最大的恒星耀斑之一，或者可能是最大的恒星耀斑。本次调查首次在 GT Mus、V841 Cen、SZ Psc 和 TWA-7 上检测到 X 射线耀斑。虽然我们检测到的大多数源都是多星系统，但其中两个是单星（YZ CMi 和 TWA-7）。在100 pc距离内的恒星源中，MAXI/GSC源的自转速度比其他源大。这表明快速旋转速度可能在产生大耀斑中发挥关键作用。结合来自文献和我们自己的数据的附近恒星和太阳的 X 射线耀斑数据，我们发现耀斑持续时间 τ 和内在 X 射线光度 LX 在 0.1-100 keV 波段内存在普遍相关性，其中 τ 和 LX 分别为 5 个和 12 个数量级。 MAXI/GSC 样本位于相关性的最高端。
Twenty-three giant flares from thirteen active stars (eight RS CVn systems, one Algol system, three dMe stars, and one young stellar object) were detected during the first two years of our all-sky X-ray monitoring with the gas propotional counters (GSC) of the Monitor of All-sky X-ray Image (MAXI). The observed parameters of all these MAXI/GSC flares are found to be at the upper ends for stellar flares with the luminosity of 1031–34erg s−1in the 2–20 keV band, the emission measure of 1054–57cm−3, thee-folding time of 1 hr to 1.5 d, and the total radiative energy released during the flare of 1034–39erg. Notably, the peak X-ray luminosity oferg s−1in the 2–20 keV band was detected in one of the flares on II Peg, which is one of the, or potentially the, largest-ever-observed in stellar flares. X-ray flares were detected from GT Mus, V841 Cen, SZ Psc, and TWA-7 for the first time in this survey. Whereas most of our detected sources are multiple-star systems, two of them are single stars (YZ CMi and TWA-7). Among the stellar sources within 100 pc distance, the MAXI/GSC sources have larger rotation velocities than the other sources. This suggests that the rapid rotation velocity may play a key role in generating large flares. Combining the X-ray flare data of nearby stars and the sun, taken from literature and our own data, we discovered a universal correlation offor the flare duration τ and the intrinsic X-ray luminosityLXin the 0.1–100 keV band, which holds for 5 and 12 orders of magnitude in τ andLX, respectively. The MAXI/GSC sample is located at the highest ends of the correlation.