行星际微透镜
Exoplanetary Microlensing
摘要：
引力微透镜发生在前景恒星恰好通过非常接近我们的视线到一个更遥远的背景恒星。前景恒星就像一个透镜，将来自源星的光分成两个图像，这两个图像通常是无法分辨的。然而，这些图像也被放大，放大的量取决于角透镜-源分离。相对透镜源运动的结果在一个随时间变化的源放大率：微透镜事件。如果前景恒星恰好拥有一颗行星，而该行星在这些图像的路径附近具有投影分离，那么该行星将进一步干扰图像，从而导致该行星的特征，短暂的签名。本章介绍了发现和描述具有引力微透镜的系外行星。该方法的理论基础进行了审查，侧重于行星摄动的现象。微透镜技术的优点和缺点进行了讨论，突出了这样一个事实，即它是敏感的低质量的行星分离刚刚超出雪线，轨道恒星位于整个银河系盘和前景隆起。本文概述了微透镜行星搜索的实践，并讨论了探测和分析行星扰动的一些挑战。本章最后回顾了迄今为止取得的成果，并讨论了微透镜行星调查的近期和长期前景。最终，微透镜对包含除水星之外的所有太阳系行星的类似物的多行星系统以及自由浮动的行星具有潜在的敏感性，并且将通过确定整个银河系行星的人口统计来提供对行星形成理论的关键测试。
英文摘要：
Gravitational microlensing occurs when a foreground star happens to pass very close to our line of sight to a more distant background star. The foreground star acts as a lens, splitting the light from the source star into two images, which are typically unresolved. However, these images are also magnified, by an amount that depends on the angular lens-source separation. The relative lens-source motion results in a time-variable source magnification: a microlensing event. If the foreground star happens to host a planet with projected separation near the paths of these images, the planet will further perturb the images, resulting in a characteristic, short-lived signature of the planet. This chapter provides an introduction to the discovery and characterization of exoplanets with gravitational microlensing. The theoretical foundation of the method is reviewed, focusing on the phenomenology of planetary perturbations. The strengths and weaknesses of the microlensing technique are discussed, highlighting the fact that it is sensitive to low-mass planets with separations just beyond the snow line, orbiting stars located throughout the Galactic disk and foreground bulge. An overview of the practice of microlensing planet searches is given, with a discussion of some of the challenges with detecting and analyzing planetary perturbations. The chapter concludes with a review of the results that have been obtained to date, and a discussion of the near and long-term prospects for microlensing planet surveys. Ultimately, microlensing is potentially sensitive to multiple-planet systems containing analogs of all the solar system planets except Mercury, as well as to free floating planets, and will provide a crucial test of planet formation theories by determining the demographics of planets throughout the Galaxy.
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