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arXiv 0704.0968astro-ph
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行星微透镜跟踪观测目标事件的选择准则

Criteria in the Selection of Target Events for Planetary Microlensing Follow-Up Observation

Cheongho Han

备注：
6 pages with 4 figures, fig 1 in JPG format
发表信息：
Astrophys.J.661:1202-1207,2007
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摘要：

为了提供选择行星透镜跟踪观测的目标事件的标准，我们研究了探测行星信号的概率随透镜放大率和源亮度可观测值的变化。在估计的概率，我们考虑的测光精度的变化，通过使用一个量定义为行星摄动的分数偏差的测光精度的比率。从这次调查中，我们发现与以前的研究一致的结果，即概率增加的放大倍率。当中心焦散引起的扰动开始出现时，在一定的放大倍数下，增加速率被提高。我们发现这种增强发生在$A\lesssim 20$的中等放大率下，这意味着即使对于中等放大率的事件，概率也很高。这种概率随着光源亮度的增加而增加。我们发现，即使在低至$A\sim 5$的放大率下，与比团簇巨星更亮的恒星相关的事件的概率也是不可忽略的。在缺乏极高放大率事件的主要目标的情况下，我们因此建议观察警报事件中具有最亮源星和最高放大率的事件。然而，由于源的大小随着亮度的增加而增加，超过一定的放大倍数，概率迅速下降，导致低质量比行星（$q\lesssim 10^{-4}$）的检测困难，从与巨恒星相关的事件的观测放大倍数$A\gtrsim 70$。

英文摘要：

To provide criteria in the selection of target events preferable for planetary lensing follow-up observations, we investigate the variation of the probability of detecting planetary signals depending on the observables of the lensing magnification and source brightness. In estimating the probability, we consider variation of the photometric precision by using a quantity defined as the ratio of the fractional deviation of the planetary perturbation to the photometric precision. From this investigation, we find consistent result from previous studies that the probability increases with the increase of the magnification. The increase rate is boosted at a certain magnification at which perturbations caused by central caustic begin to occur. We find this boost occurs at moderate magnifications of $A\lesssim 20$, implying that probability can be high even for events with moderate magnifications. The probability increases as the source brightness increases. We find that the probability of events associated with stars brighter than clump giants is not negligible even at magnifications as low as $A\sim 5$. In the absence of rare the prime target of very high-magnification events, we, therefore, recommend to observe events with brightest source stars and highest magnifications among the alerted events. Due to the increase of the source size with the increase of the brightness, however, the probability rapidly drops off beyond a certain magnification, causing detections of low mass ratio planets ($q\lesssim 10^{-4}$) difficult from the observations of events involved with giant stars with magnifications $A\gtrsim 70$.

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