Do Ultraluminous X-Ray Sources Really Contain Intermediate-Mass Black Holes?
Do Ultraluminous X-Ray Sources Really Contain Intermediate-Mass Black Holes?
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DOI：
10.1093/pasj/58.5.915
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发表时间：
2006-09
影响因子：
2.3
通讯作者：
Kiki VierdayantiShin Mineshige;K. Space;Astronautical Science;Japan Aerospace Exploration Agency;T. Kawaguchi-T.-Kawag
中科院分区：
文献类型：
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作者：
Kiki VierdayantiShin Mineshige;K. Space;Astronautical Science;Japan Aerospace Exploration Agency;T. Kawaguchi-T.-Kawag
一个悬而未决的问题仍然是超铝X射线源（ULX）是否真的包含中等质量黑洞（IMBH）。我们仔细研究了几位作者声称是IMBH强候选者的四个ULX的XMM-牛顿EPIC光谱。我们首先尝试用标准的圆盘黑体光谱模型（DBB）+幂律模型（PL）进行拟合，发现所有数据都拟合得很好，与其他方法一致。然而，我们发现，PL分量占主导地位的DBB分量在0.3至10 keV。因此，仅从次要DBB分量导出的黑洞参数是值得怀疑的。接下来，我们试图用没有PL分量的“无p盘模型”拟合相同的数据，假设有效温度分布为Teff r −p，其中r为盘半径。有趣的是，尽管少了一个自由模型参数，但我们在更高的最内层盘温度（1.8 <k Tin < 3.2keV）下获得了类似的良好拟合。更重要的是，我们得到了p = 0.5，这正是超薄（超临界）盘理论预测的值，而不是标准盘模型预测的p = 0.75。从p-自由盘模型估计的黑洞质量要小得多; M 40 M�。此外，我们应用了川口（2003，ApJ，593，69）提出的更复杂的薄盘模型，并获得了与大致一致的黑洞质量的良好拟合。因此，我们得出结论，这些ULX的中心引擎是恒星质量黑洞的超临界吸积流。
An open question remains whether Ultraluminous X-ray Sources (ULXs) really contain intermediate-mass black holes (IMBHs). We carefully investigated the XMM-Newton EPIC spectra of four ULXs that were claimed to be strong candidates of IMBHs by several authors. Wefirst triedfitting by the standard spectral model of disk blackbody (DBB) + power-law (PL), finding good fits to all of the data, in agreement with others. We, however, found that the PL component dominates the DBB component at ∼ 0.3 to 10keV. Thus, the black hole parameters derived solely from the minor DBB component are questionable. Next, we tried to fit the same data by the “p-free disk model” without the PL component, assuming an effective temperature profile of Teff ∝ r −p ,w herer is the disk radius. Interestingly, in spite of one less free-model parameter, we obtained similarly good fits with much higher innermost disk temperatures, 1.8 <k Tin < 3.2keV. More importantly, we obtained p ∼ 0.5, just the value predicted by the slim (super-critical) disk theory, rather than p =0 .75 that is expected from the standard disk model. The estimated black hole masses from the p-free disk model are much smaller; M 40 M� . Furthermore, we applied a more sophisticated slim-disk model by Kawaguchi (2003, ApJ, 593, 69), and obtained good fits with roughly consistent black hole masses. We thus conclude that the central engines of these ULXs are super-critical accretion flows to stellar-mass black holes.