Cosmological Microlensing Statistics: Variability Rates for Quasars and Gamma-Ray Burst Afterglows and Implications for Macrolensing Magnification Bias and Flux Ratios
Cosmological Microlensing Statistics: Variability Rates for Quasars and Gamma-Ray Burst Afterglows and Implications for Macrolensing Magnification Bias and Flux Ratios
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DOI：
10.1086/341481
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发表时间：
2002-03
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影响因子：
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通讯作者：
J. Wyithe;E. Turner
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作者：
J. Wyithe;E. Turner
利用有效微透镜会聚（κ）和剪切（γ）的联合分布和微透镜放大率模式，计算了类星体和γ射线暴（GRB）余辉中由于微透镜效应而变化的部分。微透镜效应在多重成像光源中很常见。我们发现，三分之一的多重成像类星体应该变化超过0.5等十年-1，因为微透镜，而10%的巨透镜伽玛射线暴余辉应该表现出超过0.5等的偏离其固有的光变曲线在第一个30天。然而，恒星的微透镜现象一般来说是罕见的，在同一时期，大约500个源中只有一个的变化超过0.5等。我们发现，大多数恒星的微透镜效应将在γ > 0.1的区域中观察到。因此，点质量透镜不能为大多数微透镜事件提供足够的描述。如果暗物质晕在致密天体中包含很大一部分质量，那么微透镜（0.5等）图像的比例就会显著上升，对于类星体大约为十分之一，对于伽马射线暴余辉大约为五分之一。宏透镜和正常的类星体图像之间的变化和适当数量的采样伽玛射线暴余辉光变曲线的比较，因此，应该发现或反驳恒星质量致密物体的存在星系晕。虽然微透镜效应会导致放大率分布偏离平滑模型，但在类星体巡天中发现透镜对宏观透镜放大率偏差的影响很小。另一方面，微透镜显著地加宽了宏观透镜图像通量比的分布。
The fraction of quasars and gamma-ray burst (GRB) afterglows that vary because of microlensing by the stellar populations of intervening elliptical/S0 galaxies is computed by combining the joint distribution of effective microlensing convergence (κ) and shear (γ) with microlensing magnification patterns. Microlensing is common in multiply imaged sources. We find that one in three multiply imaged quasars should vary by more than 0.5 mag decade-1 because of microlensing while 10% of macrolensed GRB afterglows should show a departure of more than 0.5 mag from their intrinsic light curve during the first 30 days. However, microlensing by stars is rare in general, with only one source in ~500 varying by more than 0.5 mag during the same periods. We find that most microlensing by stars will be observed in a regime where γ > 0.1. Thus, point-mass lenses do not provide an adequate description for most microlensing events. If dark matter halos contain a large fraction of mass in compact objects, the fraction of microlensed (by 0.5 mag) images rises significantly to about one in 10 for quasars and about one in five for GRB afterglows. Comparison of variability between macrolensed and normal quasar images and a moderate number of well-sampled GRB afterglow light curves should therefore discover or refute the existence of stellar mass compact objects in galaxy halos. While microlensing results in departures of the distribution of magnifications from that of a smooth model, the effect on the macrolensing magnification bias for the discovery of lenses in quasar surveys is small. On the other hand, microlensing significantly broadens the distribution of macrolensed image flux ratios.