Intraday Variability in Quasars and BL LAC Objects
Intraday Variability in Quasars and BL LAC Objects
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DOI：
10.1146/annurev.aa.33.090195.001115
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发表时间：
1995-09
影响因子：
33.3
通讯作者：
S. Wagner;A. Witzel
中科院分区：
文献类型：
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作者：
S. Wagner;A. Witzel
射电光谱平坦的活动星系核在整个波长范围内的连续通量密度在几天或更短的时间尺度上表现出显着的变化。这些快速的变化紧密地限制了发射区域的直径，并且如果变化是内在的，则意味着极高的光子密度。在无线电频率下，致密天体的通量密度可能会因星际闪烁而闪烁，而在所有的频率波段上，由恒星形成的微透镜可能会引入不是源固有的变化。我们回顾这些变化的特点，在各个电磁波段。外在机制可能会影响紧凑的河外源的光变曲线，但在不同波段记录的耀斑之间的密切相关性强烈支持的假设，即日内变化是一种内在的现象。在无线电制度的视亮度温度超过1017 K，并意味着相对论性波束非常高的多普勒…
Active galactic nuclei with flat radio spectra exhibit significant variations of continuum flux density on time scales of days or less throughout the entire wavelength range. These rapid variations tightly constrain the diameters of the emitting regions and imply extremely high photon densities if the variations are intrinsic. At radio frequencies the flux densities of compact objects may flicker due to interstellar scintillation, and in all frequency bands microlensing by stars in intervening galaxies may introduce variations that are not intrinsic to the source. We review the characteristics of these variations in the various electromagnetic bands. Extrinsic mechanisms may affect the light curves of compact extragalactic sources, but close correlations between flares recorded in different bands strongly support the assumption that intraday variability is an intrinsic phenomenon. The apparent brightness temperatures in the radio regime exceed 1017 K and imply relativistic beaming with very high Doppler ...