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arXiv 1402.4485astro-ph.HE
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天鹅座X-1的长期变异性:VI。1999-2011年能量分辨X射线变异性

Long term variability of Cygnus X-1: VI. Energy-resolved X-ray variability 1999-2011

V. Grinberg, K. Pottschmidt, M. Böck, C. Schmid, M. A. Nowak, P. Uttley, J. A. Tomsick, J. Rodriguez, N. Hell, A. Markowitz, A. Bodaghee, M. Cadolle Bel, R. E. Rothschild, J. Wilms

摘要:

我们提出了最广泛的分析傅立叶基于X射线定时属性的黑洞天鹅座X-1迄今为止,基于12年的双周监测与RXTE从1999年到2011年。我们的目标是全面研究所有光谱状态的时序行为,包括难以捉摸的过渡和极端的硬和软状态。我们讨论了光谱形状和光子能量的时间特性的依赖关系,并研究了傅立叶频率相关相干性和时间滞后与功率谱中的特征之间的相关性。我们的主要结果是:(a)在不同光谱状态下,0.125-256 Hz范围内的分数均方根显示出复杂的行为,这取决于所考虑的能量范围。它达到其最大值,而不是在硬态,但在软态中的康普顿尾部高于10千电子伏。(b)在2.1-15 keV范围内,硬态和中间态的功率谱形状以及软态的归一化都与能量密切相关。这强调了在比较不同源类型的可变性时,需要对功率谱进行能量依赖性处理,并仔细考虑能量和质量缩放,例如,黑洞双星和活动星系核极硬和极软状态下的PSD很容易与0.125-256 Hz范围内~5 keV以上的能量混淆。(c)能带之间的相干性在从中间态到软态的转变期间下降,但在软态中恢复。(d)软态和中间态的时间滞后谱在与功率谱中所见的主要可变性分量的频率相关的频率处显示出不同的特征,并且随着源软化而显示出向更高频率的相同移位。[...特别是,我们讨论了如何Cyg X-1的时间属性可以用来评估其他黑洞双星的光谱形状的变化的演变。[... [删节]

英文摘要:

We present the most extensive analysis of Fourier-based X-ray timing properties of the black hole binary Cygnus X-1 to date, based on 12 years of bi-weekly monitoring with RXTE from 1999 to 2011. Our aim is a comprehensive study of timing behavior across all spectral states, including the elusive transitions and extreme hard and soft states. We discuss the dependence of the timing properties on spectral shape and photon energy, and study correlations between Fourier-frequency dependent coherence and time lags with features in the power spectra. Our main results are: (a) The fractional rms in the 0.125-256 Hz range in different spectral states shows complex behavior that depends on the energy range considered. It reaches its maximum not in the hard state, but in the soft state in the Comptonized tail above 10 keV. (b) The shape of power spectra in hard and intermediate states and the normalization in the soft state are strongly energy dependent in the 2.1-15 keV range. This emphasizes the need for an energy-dependent treatment of power spectra and a careful consideration of energy- and mass-scaling when comparing the variability of different source types, e.g., black hole binaries and AGN. PSDs during extremely hard and extremely soft states can be easily confused for energies above ~5 keV in the 0.125-256 Hz range. (c) The coherence between energy bands drops during transitions from the intermediate into the soft state but recovers in the soft state. (d) The time lag spectra in soft and intermediate states show distinct features at frequencies related to the frequencies of the main variability components seen in the power spectra and show the same shift to higher frequencies as the source softens. [...abridged] In particular, we discuss how the timing properties of Cyg X-1 can be used to assess the evolution of variability with spectral shape in other black hole binaries. [...abridged]

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