Kepler Rotation Effects on the Binary-Lens Microlensing Events
Kepler Rotation Effects on the Binary-Lens Microlensing Events
复制标题
开普勒旋转对双透镜微透镜事件的影响
DOI：
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发表时间：
1999
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通讯作者：
Y. Kan
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文献类型：
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作者：
K. Ioka;R. Nishi;Y. Kan
研究了透镜双星的开普勒旋转对大麦哲伦云和小麦哲伦云的微透镜事件的影响。发现当透镜双星处于LMC盘或SMC盘时，旋转效应并不总是可以忽略的，当它们是自透镜的时候因此，我们认为，如果朝向晕的微透镜事件是自透镜事件，那么在分析未来双星事件时就有必要考虑旋转效应。作为一个例子，我们重新检查的1990年LMC-9事件，其中缓慢的横向速度的透镜二建议在LMC盘的微透镜事件。通过简单的分析，证明了总质量为$sim 1 M_{odot}$的透镜双星在Einstein半径交叉时间内的自转大于$sim 60^{circ}$。然而，用一个额外的参数，旋转周期，对LMC-9的拟合表明，旋转效应很小，即，在Einstein半径交叉时间期间，投影旋转角仅为5.9^{circ}（M/Modot}）^{1/4}$。这个矛盾可以解决，如果物理参数，如质量和速度，是不同的，在这个事件中，双星是近侧，或双星是非常偏心的，虽然不能从这个单一的事件得出明确的结论。如果朝向晕圈的微透镜事件是由于自透镜化，则旋转效应对其重要的二进制事件将增加，并且将获得对透镜性质的更强约束。
We investigate the effects of the Kepler rotation of lens binaries on the binary-microlensing events towards the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). It is found that the rotation effects cannot always be neglected when the lens binaries are in the LMC disk or the SMC disk, i.e., when they are self-lensing. Therefore we suggest that it will be necessary to consider the rotation effects in the analyses of the coming binary events if the microlensing events towards the halo are self-lensing. As an example, we reexamine the MACHO LMC-9 event, in which the slow transverse velocity of the lens binary suggests a microlensing event in the LMC disk. From a simple analysis, it is shown that the lens binary with total mass $sim 1M_{odot}$ rotates by more than $sim 60^{circ}$ during the Einstein radius crossing time. However, the fitting of MACHO LMC-9 with an additional parameter, the rotation period, shows that the rotation effects are small, i.e., the projected rotation angle is only $sim 5.9^{circ} (M/M_{odot})^{1/4}$ during the Einstein radius crossing time. This contradiction can be settled if the physical parameters, such as the mass and the velocity, are different in this event, the binary is nearly edge-on, or the binary is very eccentric, though definite conclusions cannot be drawn from this single event. If the microlensing events towards the halo are due to self-lensing, binary-events for which the rotation effects are important will increase and stronger constraints on the nature of the lenses will be obtained.