THE X-RAY SPECTRAL EVOLUTION OF GALACTIC BLACK HOLE X-RAY BINARIES TOWARD QUIESCENCE
THE X-RAY SPECTRAL EVOLUTION OF GALACTIC BLACK HOLE X-RAY BINARIES TOWARD QUIESCENCE
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DOI：
10.1088/0004-637x/773/1/59
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发表时间：
2013-06
期刊：
影响因子：
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通讯作者：
R. Plotkin;E. Gallo;P. Jonker
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文献类型：
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作者：
R. Plotkin;E. Gallo;P. Jonker
大多数瞬变黑洞X射线双星(BHXB)大部分时间都处于静止状态，在这种状态下，它们以极低的爱丁顿光度(我们将静止定义为归一化的爱丁顿比lx=l0.5-10kev/ledd<；10−5)与来自伴星的物质共生。在这里，我们介绍了三个BHXB系统(H1743−322，MAXI J1659−152和XTE J1752−223)在爆发后逐渐进入静止状态时的钱德拉X射线成像光谱。在一个月内进行了多次X射线观测，使我们能够跟踪每个单独系统在衰变过程中的X射线光谱演变。我们将这三个系统与其他BHXB系统进行了比较。我们证实了静态BHXB比低硬态BHXB具有更软的X射线光谱，并且静态BHXB的光谱性质不依赖于双星系统的轨道参数。然而，一旦BHXB进入静止状态，在低硬状态下观察到的X射线光子指数(Γ)与LX之间的反关联不再持续。相反，当Lx达到Γ10∼5时，∼平台的平均值<−>=2.0 8±0.0 7.因此，Lx∼10−5是静态光谱状态开始的观测激励上限。我们的结果是在不同的吸积流模型和黑洞质量尺度下讨论的。
Most transient black hole X-ray binaries (BHXBs) spend the bulk of their time in a quiescent state, where they accrete matter from their companion star at highly sub-Eddington luminosities (we define quiescence here as a normalized Eddington ratio lx = L0.5–10 keV/LEdd < 10−5). Here, we present Chandra X-ray imaging spectroscopy for three BHXB systems (H 1743−322, MAXI J1659−152, and XTE J1752−223) as they fade into quiescence following an outburst. Multiple X-ray observations were taken within one month of each other, allowing us to track each individual system's X-ray spectral evolution during its decay. We compare these three systems to other BHXB systems. We confirm that quiescent BHXBs have softer X-ray spectra than low–hard-state BHXBs, and that quiescent BHXB spectral properties show no dependence on the binary system's orbital parameters. However, the observed anti-correlation between X-ray photon index (Γ) and lx in the low–hard state does not continue once a BHXB enters quiescence. Instead, Γ plateaus to an average 〈Γ〉 = 2.08 ± 0.07 by the time lx reaches ∼10−5. lx ∼ 10−5 is thus an observationally motivated upper limit for the beginning of the quiescent spectral state. Our results are discussed in the context of different accretion flow models and across the black hole mass scale.