ANTI-CORRELATED TIME LAGS IN THE Z SOURCE GX 5-1: POSSIBLE EVIDENCE FOR A TRUNCATED ACCRETION DISK
ANTI-CORRELATED TIME LAGS IN THE Z SOURCE GX 5-1: POSSIBLE EVIDENCE FOR A TRUNCATED ACCRETION DISK
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DOI：
10.1088/0067-0049/200/2/16
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发表时间：
2012-04
期刊：
影响因子：
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通讯作者：
K. Sriram;C. Choi;A. R. Rao
中科院分区：
文献类型：
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作者：
K. Sriram;C. Choi;A. R. Rao
本文通过对不同能量X射线之间的时间差的详细研究，探讨了中子星星源GX 5-1内吸积盘的性质。利用互相关分析，我们发现了几十到几百秒量级的反相关硬和软时间滞后，对应的强度状态主要是水平分支（HB）和上正常分支。模型独立和依赖的光谱分析表明，在这些时间滞后的吸积盘的结构显着变化。东方和西方的方法被用来展开的X射线连续谱和系统的变化，观察到在软，硬光谱成分。这些变化沿着准周期振荡（QPO）频率的系统性变化，使得吸积盘的几何形状被截断变得非常明显。能谱和功率密度谱的同时研究表明，水平分支振荡（HBO）的产生与康普顿化区密切相关，而与吸积盘中的盘成分无关.我们发现，作为HBO的频率从硬顶点上HB减少，磁盘的温度增加沿着与日冕温度的增加，这是在黑洞双星中发现的变化，在那里的QPO频率的减少是伴随着磁盘温度的降低，同时在日冕温度的增加形成鲜明对比。我们讨论的背景下，在磁盘的内部区域的冠状物质的再凝聚的结果。
We investigate the nature of the inner accretion disk in the neutron star source GX 5-1 by making a detailed study of time lags between X-rays of different energies. Using the cross-correlation analysis, we found anti-correlated hard and soft time lags of the order of a few tens to a few hundred seconds and the corresponding intensity states were mostly the horizontal branch (HB) and upper normal branch. The model independent and dependent spectral analysis showed that during these time lags the structure of the accretion disk significantly varied. Both eastern and western approaches were used to unfold the X-ray continuum and systematic changes were observed in soft and hard spectral components. These changes along with a systematic shift in the frequency of quasi-periodic oscillations (QPOs) made it substantially evident that the geometry of the accretion disk is truncated. Simultaneous energy spectral and power density spectral study shows that the production of the horizontal branch oscillations (HBOs) is closely related to the Comptonizing region rather than the disk component in the accretion disk. We found that as the HBO frequency decreases from the hard apex to upper HB, the disk temperature increases along with an increase in the coronal temperature, which is in sharp contrast with the changes found in black hole binaries where the decrease in the QPO frequency is accompanied by a decrease in the disk temperature and a simultaneous increase in the coronal temperature. We discuss the results in the context of re-condensation of coronal material in the inner region of the disk.