Binary Lenses: The Power of Two

该项目致力于解释在银河系光晕中寻找大质量致密晕天体(MACHO)时引力微透镜事件的信号。如果晕暗物质的很大一部分由MACHO组成，监测计划应该会发现比已知恒星群所能产生的更多的微透镜事件。在过去的15年里，已经发现了2500多个微透镜事件。目前的发现率约为每年600人，随着新的监测项目的开始，这一速度将很快增加。大多数灯光曲线都是标准的点光源、点透镜类型。这些“香草”光曲线是高度退化的：在没有清晰视差效果的情况下，只能估计镜头质量、速度和位置的组合。因此，要确定与MACHO相关的贡献，必须依靠统计研究。尽管第一代监测程序的结果对男性比例施加了限制，但结果仍然具有高度的不确定性。另一方面，双镜头光线曲线包含更多信息。在理想情况下，可以测量透镜的位置、速度和质量，并可以限制双星的轨道间距和质量比。因此，双目透镜可以提供强大的诊断能力。那些位于源星系中的星系可能被识别出来，并从晕中暗质量的特征中适当地减去。双星MACHO(如果存在)是可以识别的，而编码在双目透镜光曲线中的丰富信息为测量单个MACHO的性质提供了令人兴奋的前景。通过研究单个事件获得的力量被放大到双目透镜光曲线的集合。这是因为光曲线形状的多样性及其与透镜物理参数的联系为一致性检查提供了多种机会，同时也探索了透镜群体中二元属性的分布。在这里，Di Stefano博士和合作者将开发必要的工具，在过去、现在和未来的监测程序收集的数据中系统地寻找和解释二元透镜事件。通过将这项工作应用于几个小组收集的数据，已知的双目透镜事件的数量可能会翻一番。最重要的是，这些方法将适用于来自所有其他监测项目的数据，包括广域调查、全景观测望远镜和快速反应系统(PAN-STARRS)和大型天气观测望远镜(LSST)。这项工作还将解决图像可变性的自动检测和分类问题，这在生物学等领域有着广泛的应用。研究生和本科生将在工作的每个阶段发挥重要作用。Di Stefano博士还参与了与剑桥公立学校的一项外展计划，其中将包括与K-8年级的学生讨论这项工作。

This project is concerned with interpreting the signals of gravitational microlensing events in searches for Massive Compact Halo Objects (MACHOs) in the halo of the Milky Way. If a significant fraction of halo dark matter consists of MACHOs, monitoring programs should discover more microlensing events than can be generated by known stellar populations. More than 2500 microlensing events have been discovered during the past 15 years. The present rate of discovery is roughly 600 per year, and will soon increase as new monitoring programs begin. Most light curves are of the standard point-source, point-lens type. These "vanilla" light curves are highly degenerate: in the absence of clear parallax effects, only a combination of the lens mass, speed, and position can be estimated. To determine the contribution associated with MACHOs, one must therefore rely on statistical studies. Although results from the first generation of monitoring programs place limits on the MACHO fraction, the results are still highly uncertain.Binary lens light curves, on the other hand, contain more information. Under ideal circumstances the position, speed, and mass of the lens can be measured, and limits can be placed on the binary's orbital separation and mass ratio. Binary lenses can therefore provide powerful diagnostics. Those located in the source galaxy can potentially be identified and appropriately subtracted from the signature of dark masses in the Halo. Binary MACHOs(if they exist) can be identified, and the wealth of information coded in binary-lens light curves presents the exciting prospect of measuring the properties of individual MACHOs.The power gained through studying individual events is magnified for an ensemble of binary-lens light curves. This is because the variety of light curve shapes and their connection to the physical parameters of the lens provide multiple opportunities for consistency checks, while also probing the distribution of binary properties among the lens population.Here, Dr. Di Stefano and collaborators will develop the necessary tools to systematically find and interpret binary lens events in the data collected by monitoring programs of the past, present, and future. By applying this work to data collected by several groups, the number of known binary-lens events will likely be doubled. Most important, these methods will be adaptable to data from all other monitoring programs, including the wide-field surveys, the Panoramic Survey Telescope & Rapid Response System (Pan-STARRS), and the Large Synoptic Survey Telescope (LSST).This work will also address the automated detection and classification of variability in images, which has broad application, to, e.g., biology. Graduate and undergraduate students will play important roles at every stage of the work. Dr. Di Stefano is also involved in an outreach program with the Cambridge public schools which will include discussions of this work with students in grades K-8.