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Study of the Galactic Structure using Astrometric Microlensing

利用天体微透镜研究银河结构

基本信息

批准号：
15540240
负责人：
OHNISHI Kouji
金额：
$ 1.92万
依托单位：
Nagano National College of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2006
项目状态：
已结题

项目摘要

Astrometric Microlensing(the positional shift due to gravitational lens effect by stars, MACHOs and the Galaxy) is useful to study the structure of our galaxy.(1)Astrometric study of MACHO halo distribution in our GalaxyWe estimated the optical depth and event rate of micro-arcsecond level astrometric microlensing for the stars outside our galaxy caused by MACHOs. For the stars in the LMC and the SMC, the optical depth of 1 micro-arcsecond detection threshold is on the order of 0.1 and the event rate of the induced proper motion of 1 micro-arcsecond/year is on the order of 0.001/yr. They depend on the distribution of lenses and sources. This poses a constraint on the expected probability of photometric self-lensing in LMC and SMC.(2)Macrolens toward the Galactic CenterThe motion of Sgr A^* has been measured by referring to QSOs in the direction of Galactic Center. The QSOs referred in the observations are close to Sgr A^* on the celestial sphere. This means that we observe these QSOs t … More hrough the core, the bulge, and the disk of the Galaxy where stars are very densely distributed. Therefore, the observed position of QSOs may vary due to the gravitational deflection by foreground objects, e.g. stars and our Galaxy itself. We consider the macro lens effect, the collective gravitational deflection by the core and the bulge of the Galaxy. Its magnitude is the order of 1 micro-arcsecond/yr. However, this effect is important because it has a secular component. The measurement of these effects will provide us valuable information on the density and mass function of the Galactic Center.(3)Discovery of the cool planet through gravitational lensingGravitational Microlensing events can reveal extraSolar planet orbiting the foreground lending stars. We found the cool planet of 5.5 Earth masses by MOA project for investigating the structure in our galaxy using photometric microlensing observation.(4)TAGO Event.We report the observation of the first gravitational microlensing event on a very close(1kpc) bright star in a sparse stellar field. A. Tago discovered this event on 31 October 2006 towards the Cassiopeia constellation. The light curve analyses indicate that this event was caused by the gravitational microlensing rather than a genuine variable star. The provability of such a high magnification in nearby stars is much small. This may be just a good luck, or true event rate is higher than expected due to (unknown) low mass star distribution function on disk structure in our galaxy. Less

天体测量微透镜(由于恒星、MACHO和银河系引力透镜效应引起的位置移动)对研究银河系的结构是有用的。(1)银河系中大磁晕分布的天体测量研究我们估计了由MACHO引起的银河系外恒星微弧二级天体测量微透镜的光学厚度和事件发生率。对于大尺度和小尺度尺度上的恒星，1微角秒探测阈值的光学厚度约为0.1，1微角秒/年的诱发自行事件率约为0.001/年。它们取决于镜片和光源的分布。这限制了LMC和SMC中光度自透镜的预期概率。(2)宏透镜朝向银心通过参照类星体在银心方向上测量了SgrA^*的运动。观测中提到的类星体在天球上接近SgrA^*。这意味着我们在…中观察到了这些类星体更多的是通过星系的核心、凸起和圆盘，那里的恒星非常密集地分布。因此，观测到的类星体的位置可能会因为前景物体的引力偏转而变化，例如恒星和我们的星系本身。我们考虑了宏观透镜效应、地核的集体引力偏转和银河系的隆起。其量级是1微角秒/年的数量级。然而，这种影响很重要，因为它有一个长期的组成部分。对这些效应的测量将为我们提供关于银河系中心密度和质量函数的有价值的信息。(3)通过引力透镜发现这颗凉爽的行星引力微透镜事件可以揭示太阳系外的行星围绕前景借出的恒星运行。我们通过MOA计划发现了这颗质量为5.5地球的冷行星，用于研究我们银河系的光度微透镜观测。(4)Tago Event.我们报道了在稀疏恒星场中观测到的一颗非常近(1kpc)明亮恒星上第一次引力微透镜事件。答：Tago于2006年10月31日在仙后座发现了这一现象。光曲线分析表明，这一事件是由引力微透镜引起的，而不是真正的变星。如此高的放大率在附近恒星中的可证明性要小得多。这可能只是一种运气，或者由于(未知的)低质量恒星在我们银河系的盘状结构上的分布函数，真实的事故率比预期的要高。较少