Comparing Spectral Models for ULXs with NGC 4517 ULX1
Comparing Spectral Models for ULXs with NGC 4517 ULX1
复制标题
比较 ULX 与 NGC 4517 ULX1 的光谱模型
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
A. Fabian
中科院分区：
文献类型：
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作者：
J. Gladstone;C. Done;D. Walton;T. Roberts;M. Middleton;M. Caballero;A. Fabian
我们展示了ngc4517中一个超亮x射线候选源的高质量xmm -牛顿光谱。与其他高质量的ULX光谱一样，在~6 keV处观察到光谱的下降。为了提供一个直接的比较，我们应用了最近的圆盘反射和这一特征的复合解释，并发现它们提供了当前数据的统计等效表示。我们发现，反射模型要求吸积盘具有高度的超级太阳铁丰度，而复合模型要求低温复合电子，并且日冕具有光学厚度。详细讨论了这些物理要求，并强调了物理驱动的情景，其中每个模型都可以被认为是对观测到的排放的可行解释。通过将这两种解释的考虑扩展到高能量，我们证明了在试图区分它们时，对~10 keV以上能量的ulx的观测应该是非常有用的。以目前的仪器，只能对M82 X-1进行这些观测，但未来的高角分辨率硬x射线成像光谱仪，如硬x射线成像系统，将在Astro-H上飞行，应该在解决这个问题上走很长的路。
We present the previously unanalysed high quality XMM-Newton spectrum of an ultraluminous X-ray source candidate in NGC 4517. As with other high quality ULX spectra, a downturn in the spectrum is observed at ~6 keV. Both of the recent disc reflection and Comptonisation interpretations of this feature are applied, in order to present a direct comparison, and are found to provide statistically equivalent representations of the current data. We find that the reflection model requires the accretion disc to have a highly super-solar iron abundance, while the Comptonisation model requires low temperature Comptonising electrons, and for the corona to be optically thick. These physical requirements are discussed in detail, and physically motivated scenarios are highlighted in which each model can be considered a viable explanation for the observed emission. By extending our consideration of these two interpretations to high energies, we demonstrate that observations of ULXs at energies above ~10 keV should be extremely useful when attempting to distinguish between them. With current instrumentation, it is only viable to perform these observations for M82 X-1, but future high angular resolution hard X-ray imaging spectrometers, such as the Hard X-ray Imaging System due to fly on Astro-H, should go a long way to resolving this issue.