超铝状态
The Ultraluminous State
摘要：
我们通过对ULX的光谱形状进行详细的调查，重新审视了ULX的性质问题，使用了XMM-Newton公共档案中最高质量的X射线数据。我们确认，简单的光谱模型通常用于分析和解释的ULXs（幂律连续和多色盘黑体模型）是不够的，在面对这样的高质量的数据。相反，我们发现两个几乎无处不在的功能在频谱中：一个软过剩和翻转在3keV以上的能量的频谱。我们研究了一系列更物理的模型来描述这些数据。我们发现，光盘加康普顿日冕模型拟合数据很好，但派生的日冕是冷的，光学厚（τ~5 - 30）。我们认为，这些观察到的光盘的温度是不是一个很好的指标的黑洞质量的强大的，光学厚日冕排水能量从内部光盘，并掩盖它。我们估计的内在（无日冕）光盘温度，并证明在大多数情况下，它位于恒星质量的黑洞的制度。这些天体的光谱范围从类似于银河双星中最高质量吸积率状态的光谱，到那些明显具有两个峰值的光谱，一个峰值的能量低于1千电子伏（来自外部未康普顿化的圆盘），另一个峰值的能量高于3千电子伏（来自康普顿化的内部圆盘）。然而，一些ULX有一个显着冷却器校正光盘温度，我们认为，这些是最极端的恒星质量黑洞吸积物，其中一个巨大的风完全包裹内部光盘区域，创造一个凉爽的光球。我们的结论是，ULXs为我们提供了一个观测模板之间的过渡爱丁顿和超爱丁顿吸积流，后者占据了一个新的超铝吸积状态。
英文摘要：
(Abridged) We revisit the question of the nature of ULXs through a detailed investigation of their spectral shape, using the highest quality X-ray data available in the XMM-Newton public archives. We confirm that simple spectral models commonly used for the analysis and interpretation of ULXs (power-law continuum and multi-colour disc blackbody models) are inadequate in the face of such high quality data. Instead we find two near ubiquitous features in the spectrum: a soft excess and a roll-over in the spectrum at energies above 3keV. We investigate a range of more physical models to describe these data. We find that disc plus Comptonised corona models fit the data well, but the derived corona is cool, and optically thick (tau ~ 5-30). We argue that these observed disc temperatures are not a good indicator of the black hole mass as the powerful, optically thick corona drains energy from the inner disc, and obscures it. We estimate the intrinsic (corona-less) disc temperature, and demonstrate that in most cases it lies in the regime of stellar mass black holes. These objects have spectra which range from those similar to the highest mass accretion rate states in Galactic binaries, to those which clearly have two peaks, one at energies below 1 keV (from the outer, unComptonised disc) and one above 3 keV (from the Comptonised, inner disc). However, a few ULXs have a significantly cooler corrected disc temperature; we suggest that these are the most extreme stellar mass black hole accretors, in which a massive wind completely envelopes the inner disc regions, creating a cool photosphere. We conclude that ULXs provide us with an observational template for the transition between Eddington and super-Eddington accretion flows, with the latter occupying a new ultraluminous accretion state.
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