A new characterization of the Compton process in the ULX spectra
A new characterization of the Compton process in the ULX spectra
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DOI：
10.1002/asna.201612333
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发表时间：
2015-11
影响因子：
0.9
通讯作者：
S. Kobayashi;K. Nakazawa;K. Y. U. O. Tokyo;Riken
中科院分区：
文献类型：
--
作者：
S. Kobayashi;K. Nakazawa;K. Y. U. O. Tokyo;Riken
试图建立ULX（超亮x射线源）天体光谱的统一描述，包括它们的幂律（PL）状态和盘状状态。在解释这两种状态的光谱模型中，本文采用了多色光盘（MCD）发射及其热复合（THC）的光谱模型。该模型应用于Suzaku、XMM-Newton和Nustar获得的多个ulx数据集。该模型很好地解释了冷盘（内半径温度为0.2-0.5 keV）和冷厚（电子温度为1-3 keV，光学厚度~10）电晕的所有光谱，无论光谱状态如何。拟合结果可以用两个新的参数来表征。一个是Q（定义为电子温度除以内部半径温度），它描述了日冕电子的康普顿冷却和引力加热之间的平衡，另一个是F，即日冕覆盖MCD的比例。这里，F是根据直接可见的圆盘光度占总辐射的百分比计算的。然后，发现pl态的光谱为Q~10和F~0.5，而盘状态的光谱为Q~3和F~1。因此，这两种状态在Q和f方面是明显分开的。所获得的结果被用来论证它们在高质量（几十到几百个太阳质量）黑洞方面的解释。
Attempts were made to construct a unified description of the spectra of ULX (Ultra Luminous X-ray source) objects, including their Power-Law (PL) state and Disk-like state. Among spectral models proposed to explain either state, the present work adopts the one which combines multi-color disk (MCD) emission and its thermal Comptonization (THC). This model was applied to several datasets of ULXs obtained by Suzaku, XMM-Newton, and Nustar. The model well explains all the spectra, regardless of the spectral states, in terms of a cool disk (inner radius temperature of 0.2-0.5 keV) and a cool thick (electron temperature of 1-3 keV, and optical thickness ~10) corona. The fit results can be characterized by two new parameters. One is Q (defined as the electron temerature divided by the inner radius temperature) which describes balance between the Compton cooling and gravitational heating of the coronal electrons, while the other is F, namely, the covering fraction of the MCD by the corona. Here, F is calculated from the percentage of the directly-visible disk luminosity in the total radiation. Then, the PL-state spectra have been found to show Q~10 and F~0.5, while those of the Disk-like state Q~3 and F~1. Thus, the two states are clearly separated in terms of Q and F. The obtained results are employed to argue for their interpretation in terms of high-mass (several tens to several hundreds solar masses) black holes.