X-ray variability with spectral state transitions in NS-LMXBs observed with MAXI/GSC and Swift/BAT
X-ray variability with spectral state transitions in NS-LMXBs observed with MAXI/GSC and Swift/BAT
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DOI：
10.1093/pasj/psv060
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发表时间：
2015-06
影响因子：
2.3
通讯作者：
K. Asai;T. Mihara;M. Matsuoka;M. Sugizaki
中科院分区：
文献类型：
--
作者：
K. Asai;T. Mihara;M. Matsuoka;M. Sugizaki
利用MAXI/GSC （Gas Slit Camera）和Swift/BAT （Burst Alert Telescope）的单日箱光曲线，研究了含有一颗中子星的明亮低质量x射线双星的x射线随光谱状态跃变的变化。四个光源（4U 1636$- 536, 4U 1705$- 44, 4U 1608$- 52和GS 1826$- 238）表现出随光谱状态转变的小幅度x射线变化。这种“迷你爆发”的特点是振幅较小（几次），持续时间较短（不到几十天），而不是“正常爆发”。Mineshige和Osaki （PASJ, 37,1, 1985）的圆盘不稳定性理论模型预测了大振幅爆发和小振幅变化。我们将正常爆发解释为该模型的前者预测，而将小型爆发解释为后者预测。在这里，参考理论工作，我们也可以将这种小型突出称为“咕噜式突出”。我们认为，类似的变化持续几十天而没有光谱状态转变，这在硬状态下经常观察到，可能是重复的小爆发。
X-ray variabilities with spectral state transitions in bright low mass X-ray binaries containing a neutron star are investigated by using the one-day bin light curves of MAXI/GSC (Gas Slit Camera) and Swift/BAT (Burst Alert Telescope). Four sources (4U 1636$-$536, 4U 1705$-$44, 4U 1608$-$52, and GS 1826$-$238) exhibited small-amplitude X-ray variabilities with spectral state transitions. Such "mini-outbursts" were characterized by smaller amplitudes (several times) and shorter duration (less than several tens of days) than those of "normal outbursts." Theoretical model of disk instability by Mineshige and Osaki (PASJ, 37, 1, 1985) predicts both large-amplitude outbursts and small-amplitude variabilities. We interpret the normal outbursts as the former prediction of this model, and the mini-outbursts as the latter. Here, we can also call the mini-outburst as "purr-type outburst" referring to theoretical work. We suggest that similar variabilities lasting for several tens of days without spectral state transitions, which are often observed in the hard state, may be a repeat of mini-outbursts.