ASTROMETRIC IMAGE CENTROID DISPLACEMENTS DUE TO GRAVITATIONAL MICROLENSING BY THE ELLIS WORMHOLE
ASTROMETRIC IMAGE CENTROID DISPLACEMENTS DUE TO GRAVITATIONAL MICROLENSING BY THE ELLIS WORMHOLE
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DOI：
10.1088/0004-637x/740/2/121
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发表时间：
2011-07
期刊：
影响因子：
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通讯作者：
Y. Toki;Takao Kitamura;H. Asada;F. Abe
中科院分区：
文献类型：
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作者：
Y. Toki;Takao Kitamura;H. Asada;F. Abe
继续在早期出版的工作开始，我们研究的引力微透镜效应的埃利斯虫洞在弱场限制。首先，我们找到一个合适的坐标变换，这样的透镜方程和透镜像位置的解析表达式可以变得简单得多。其次，我们证明了弱场透镜在Ellis虫洞附近总是出现两个像。利用这些分析结果，我们讨论了由于引力微透镜的埃利斯虫洞的天体测量图像的质心位移。由Ellis虫洞产生的天体测量像质心轨迹不同于由Schwarzschild度规表示的标准球面透镜天体测量像质心轨迹。当碰撞参数和爱因斯坦环半径相同时，Ellis虫洞透镜引起的像质异常偏移小于Schwarzschild透镜引起的像质异常偏移。因此，Ellis虫洞的透镜图像质心移动较慢。这样的差异虽然很小，但原则上将适用于通过使用未来的高精度天体测量观测来检测或限制埃利斯虫洞。特别是，图像质心位置给我们提供了额外的信息，从而可以部分打破光度微透镜中存在的参数退化。如果我们的银河系拥有一个喉径大于105公里的虫洞，那么这种异常位移达到了几微弧秒的量级。例如，当源切向移动到爱因斯坦环时，由埃利斯虫洞引起的图像质心的最大位置偏移由爱因斯坦环半径归一化为0.18。对于相同的源轨迹，具有相同爱因斯坦环半径的埃利斯虫洞透镜和史瓦西透镜的质心位移之间的最大差值为-0.16（以爱因斯坦半径为单位），其中负值意味着埃利斯虫洞透镜的天体测量位移小于史瓦西透镜。
Continuing work initiated in an earlier publication, we study the gravitational microlensing effects of the Ellis wormhole in the weak-field limit. First, we find a suitable coordinate transformation, such that the lens equation and analytic expressions of the lensed image positions can become much simpler. Second, we prove that two images always appear for the weak-field lens by the Ellis wormhole. By using these analytic results, we discuss astrometric image centroid displacements due to gravitational microlensing by the Ellis wormhole. The astrometric image centroid trajectory by the Ellis wormhole is different from the standard one by a spherical lensing object that is expressed by the Schwarzschild metric. The anomalous shift of the image centroid by the Ellis wormhole lens is smaller than that by the Schwarzschild lens, provided that the impact parameter and the Einstein ring radius are the same. Therefore, the lensed image centroid by the Ellis wormhole moves slower. Such a difference, although it is very small, will be, in principle, applicable for detecting or constraining the Ellis wormhole by using future high-precision astrometry observations. In particular, the image centroid position gives us additional information, so that the parameter degeneracy existing in photometric microlensing can be partially broken. The anomalous shift reaches the order of a few micro arcseconds, if our galaxy hosts a wormhole with throat radius larger than 105 km. When the source moves tangentially to the Einstein ring, for instance, the maximum position shift of the image centroid by the Ellis wormhole is 0.18 normalized by the Einstein ring radius. For the same source trajectory, the maximum difference between the centroid displacement by the Ellis wormhole lens and that by the Schwarzschild one with the same Einstein ring radius is −0.16 in the units of the Einstein radius, where the negative means that the astrometric displacement by the Ellis wormhole lens is smaller than that by the Schwarzschild one.