Where are the binary source gravitational microlensing events? II
Where are the binary source gravitational microlensing events? II
复制标题
双源引力微透镜事件在哪里？
DOI：
--
复制
发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Y. Jeong
中科院分区：
文献类型：
--
作者：
C. Han;Y. Jeong
目前，已经报告了6个候选二元透镜事件，而仅报告了单个候选二元源事件。为了解释双星源事件的罕见性，Dominik指出，对于典型的双星源事件，组成源星之间的间隔非常大，导致组成双星源星之间的撞击参数差异很大。在这些情况下，高度放大的源星星的光变曲线几乎不受来自另一颗星星的光的影响，使得观测到的双源光变曲线难以与单源透镜事件的光变曲线区分开来。在本文中，我们确定的事件与相似的源星星放大的比例是高达$sim 8%$，从而表明，非常低的检测率为二进制源事件不能解释单独的这种效果。通过对二进制源事件进行逼真的模拟，我们发现由于各种其他原因，二进制源事件的一个重要部分被额外错过。首先，如果组成恒星之间的通量比非常大，那么明亮的星星的光变曲线几乎不会受到来自暗淡的星星的光的影响。第二，如果分离太小，双星源星的行为就像一个单一的星星，使它很难从一个单一的事件分离双星源事件。最后，虽然检测到二元源事件的概率随着源分离的增加而增加，但仍有一部分二元源事件将被错过，因为这些事件的光变曲线将模仿具有较长时间尺度和较大影响参数值的单源事件的光变曲线。
Currently, 6 candidate binary lens events have been reported, while only a single candidate binary source event has been reported. To account for the rarity of binary source events, Dominik pointed out that for a typical binary source event the separation between the component source stars is very large, resulting in large difference in impact parameters between the component binary source stars. In these cases, the light curve of the highly amplified source star is barely affected by the light from the other star, making the observed binary source light curve difficult to distinguish from that of a single source lensing event. In this paper, we determine the fraction of events with similar source star amplifications is as much as $sim 8%$, and thus show that the very low detection rate for binary source events cannot be explained by this effect alone. By carrying out realistic simulations of binary source events, we find that a significant fraction of binary source events are additionally missed from detection due to various other reasons. First, if the flux ratio between the component stars is very large, the light curve of the bright star is hardly affected by the light from the faint star. Second, if the separation is too small, the binary source stars behave like a single star, making it difficult to separate the binary source event from a single event. Finally, although the probability of detecting binary source events increases as the source separation increases, still some fraction of binary source events will be missed because the light curves of these events will mimic those of single source events with longer timescales and larger values of the impact parameter.