The effects of redshifts and focusing on the spectrum of an accretion disk around a Kerr black hole
The effects of redshifts and focusing on the spectrum of an accretion disk around a Kerr black hole
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DOI：
10.1086/154033
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发表时间：
1975-12
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影响因子：
--
通讯作者：
C. Cunningham
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文献类型：
--
作者：
C. Cunningham
黑洞周围的吸积盘产生的x射线光谱明显受到多普勒频移、引力红移和引力透镜效应的影响。这些影响可以用“传递函数”来描述，将其折叠成任何假设的在磁盘表面发射的光谱，以得到在远离磁盘的不同位置观察到的光谱。本文对a/M=0和0.9981的Kerr黑洞建立了这样一个传递函数，并将其制成表格。传递函数在很大程度上取决于观测者的极角：与靠近圆盘极轴的观测者相比，靠近圆盘平面的观测者看到来自其热内部区域的辐射偏移较少，并且具有更大的立体角。因此，赤道观测者在高能量下看到的光谱要比极地观测者难得多。这种效应在角动量较大的黑洞中更为明显。(AIP)
The spectrum of X-rays produced by an accretion disk around a black hole is influenced markedly by Doppler shifts, gravitational redshifts, and the gravitational lens effect. These influences can be described by a ''transfer function,'' which one folds into any assumed spectrum emitted on the disk's surface to get the spectrum observed at various locations far from the disk. This paper formulates such a transfer function and tabulates it for Kerr black holes of a/M=0 and 0.9981. The transfer function depends strongly on the polar angle of the observer: An observer near the plane of the disk sees radiation from its hot inner regions to be less reshifted and to subtend a greater solid angle than does an observer near the disk's polar axis. Consequently, the equatorial observer sees a much harder spectrum at high energies than does the polar observer. This effect is more pronounced for black holes of larger angular momentum. (AIP)