COMPTONIZED PHOTON SPECTRA OF SUPERCRITICAL BLACK HOLE ACCRETION FLOWS WITH APPLICATION TO ULTRALUMINOUS X-RAY SOURCES
COMPTONIZED PHOTON SPECTRA OF SUPERCRITICAL BLACK HOLE ACCRETION FLOWS WITH APPLICATION TO ULTRALUMINOUS X-RAY SOURCES
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DOI：
10.1088/0004-637x/752/1/18
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发表时间：
2012-06
期刊：
影响因子：
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通讯作者：
T. Kawashima;K. Ohsuga;S. Mineshige;T. Yoshida;D. Heinzeller;R. Matsumoto
中科院分区：
文献类型：
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作者：
T. Kawashima;K. Ohsuga;S. Mineshige;T. Yoshida;D. Heinzeller;R. Matsumoto
通过对轴对称辐射流体动力学模拟的结果进行后处理，使用蒙特卡罗方法计算超临界黑洞吸积流的辐射谱。我们考虑了热/体康普顿化、自由-自由吸收和光子捕获。我们发现，在黑洞附近的漏斗壁处出现了一个激波加热区域（∼108 K），其中超音速流入被势的离心势垒反射。尽管由于光子捕获，大多数上散射高于 40 keV 的光子被黑洞吞噬，但热和体康普顿化都显着硬化了光子光谱。当黑洞的吸积率约为 200LE/c2（其中 LE 是爱丁顿光度）时，光谱具有幂律分量，通过激波加热区域中光子的上散射，该幂律分量可扩展至 ∼10 keV。在较高的质量吸积率下，由于射流周围的密集流出中的冷电子对光子进行向下散射，光谱会翻转约 5 keV。我们的结果与超亮 X 射线源的光谱特征一致，后者通常显示出延伸至 10 keV 的硬幂律分量或大约 5 keV 的翻转。我们发现NGC 1313 X-2的光谱与低视角（i = 10°–20°）观测到的高吸积率（）源的数值计算得到的光谱非常相似。我们的数值结果还表明，超临界吸积恒星质量黑洞 (10 M☉) 的正面光度可以显着超过 1040 erg s−1。
Radiation spectra of supercritical black hole accretion flows are computed using a Monte Carlo method by post-processing the results of axisymmetric radiation hydrodynamic simulations. We take into account thermal/bulk Comptonization, free–free absorption, and photon trapping. We found that a shock-heated region (∼108 K) appears at the funnel wall near the black hole where the supersonic inflow is reflected by the centrifugal barrier of the potential. Both thermal and bulk Comptonization significantly harden photon spectra although most of the photons upscattered above 40 keV are swallowed by the black hole due to the photon trapping. When the accretion rate onto the black hole is ≈ 200LE/c2, where LE is the Eddington luminosity, the spectrum has a power-law component which extends up to ∼10 keV by upscattering of photons in the shock-heated region. In higher mass accretion rates, the spectra roll over around 5 keV due to downscattering of the photons by cool electrons in the dense outflow surrounding the jet. Our results are consistent with the spectral features of ultraluminous X-ray sources, which typically show either a hard power-law component extending up to 10 keV or a rollover around 5 keV. We found that the spectrum of NGC 1313 X-2 is quite similar to the spectrum numerically obtained for high accretion rate () source observed with low viewing angle (i = 10°–20°). Our numerical results also demonstrate that the face-on luminosity of supercritically accreting stellar mass black holes (10 M☉) can significantly exceed 1040 erg s−1.