Near-Field Microlensing from Wide-Field Surveys
Near-Field Microlensing from Wide-Field Surveys
复制标题
广域测量的近场微透镜
DOI：
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发表时间：
2007
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通讯作者：
C. Han
中科院分区：
文献类型：
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作者：
C. Han
我们估计了全天空观测中预期的近场微透镜事件的发生率，并调查了事件的性质。假设透镜体是由恒星组成，我们对事件率的估计范围是从Vlim = 12的巡天的Γtot <$0.1 yr −1到Vlim = 18的巡天的Γtot <$23 yr −1。我们发现，到源星星和透镜的平均距离变化很大程度上取决于星等的限制，而事件的时间尺度和透镜源的横向速度的依赖性是弱的。我们还发现，在Vlim = 18的观测中，预期事件的平均透镜-源自行将是10 μ m × 40 mas yr-1，并且随着震级极限变低，该值进一步增加，这意味着在透镜放大数年后进行的高分辨率后续观测中，可以分辨出相当一部分近场事件的源和透镜。从事件特征随天区位置变化的研究中，我们发现，随着天区银河系纬度的增加，到源星和透镜的平均距离变短，透镜-源横向速度增加，时间尺度变短。由于事件集中在银道面附近，我们发现，在B为30°的区域中，将检测到大约50%的事件。
We estimate the rate of near-field microlensing events expected from all-sky surveys and investigate the properties of the events. Under the assumption that lenses are composed of stars, our estimation of the event rate ranges from Γtot ∼ 0.1 yr −1 for a survey with a magnitude limit of Vlim = 12 to Γtot ∼ 23 yr −1 for a survey with Vlim = 18. We find that the average distances to the source star and lens vary considerably depending on the magnitude limit, while the dependencies of the event timescale and lens-source transverse speed are weak. We also find that the average lens-source proper motion of events expected from a survey with Vlim = 18 would be ⟨ μ ⟩ ≳ 40 mas yr −1, and the value further increases as the magnitude limit becomes lower, implying that the source and lens of a significant fraction of near-field events can be resolved from high-resolution follow-up observations conducted several years after the lensing magnification. From the investigation of the variation of the event characteristics depending on the position of the sky, we find that the average distances to source stars and lenses become shorter, the lens-source transverse speed increases, and the timescale becomes shorter as the Galactic latitude of the field increases. Because of the concentration of events near the Galactic plane, we find that ≳50% of events would be detected in the field with b ⩽ 30°.