黑洞双星GRS 1915+105光子指数饱和的发现
Discovery of photon index saturation in the black hole binary GRS 1915+105
摘要：
本文研究了银河系黑洞双星GRS 1915+105在软硬态转换过程中的光谱、时间特性和质量吸积率之间的相关性。我们分析了所有的过渡事件，从这个来源观察到的RXTE，与赖尔射电望远镜（RT）的观测协调。我们表明，GRS 1915+105在所有这些光谱状态下的宽带能谱可以通过两个体运动康普顿化（BMC）分量充分呈现：硬组分（BMC 1，光子指数Gamma_1=1.7-3.0），具有高能量和软热分量的转换（BMC 2，Gamma_2=2.7-4.2），特征色温<1 keV，以及红偏铁线（LAOR）分量。我们还提出了可观察到的指数和磁盘的“种子”组件的正常化之间的相关性。使用“种子”磁盘归一化，这大概是成比例的磁盘中的质量吸积率，是至关重要的建立在过渡到软态的指数饱和效应。我们发现软和硬光谱分量的光子指数饱和值分别为4.2和3。我们提出了一个物理模型，解释了索引种子光子归一化相关性。我们认为，硬分量（BMC 1）的折射率饱和效应是由于BH附近会聚入流中的软光子康普顿化，而软分量的折射率饱和效应是由于质量吸积率增大时过渡层中的物质积累。除了我们的光谱模型组件，我们还发现了一个很强的“黑体”颠簸的色温约为4.5千电子伏的中间和软态的八个观测功能。我们讨论了这种“黑体”排放的可能来源。
英文摘要：
We present a study of the correlations between spectral, timing properties and mass accretion rate observed in X-rays from the Galactic Black Hole (BH) binary GRS 1915+105 during the transition between hard and soft states. We analyze all transition episodes from this source observed with RXTE, coordinated with Ryle Radio Telescope (RT) observations. We show that broad-band energy spectra of GRS 1915+105 during all these spectral states can be adequately presented by two Bulk Motion Comptonization (BMC) components: a hard component (BMC1, photon index Gamma_1=1.7-3.0) with turnover at high energies and soft thermal component (BMC2, Gamma_2=2.7-4.2) with characteristic color temperature <1 keV, and the redskewed iron line (LAOR) component. We also present observable correlations between the index and the normalization of the disk "seed" component. The use of "seed" disk normalization, which is presumably proportional to mass accretion rate in the disk, is crucial to establish the index saturation effect during the transition to the soft state. We discovered the photon index saturation of the soft and hard spectral components at values of 4.2 and 3 respectively. We present a physical model which explains the index-seed photon normalization correlations. We argue that the index saturation effect of the hard component (BMC1) is due to the soft photon Comptonization in the converging inflow close to BH and that of soft component is due to matter accumulation in the transition layer when mass accretion rate increases. In addition to our spectral model components we also find a strong feature of "blackbody-like" bump which color temperature is about 4.5 keV in eight observations of the intermediate and soft states. We discuss a possible origin of this "blackbody-like" emission.
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