Binary Lenses: The Power of Two

该项目涉及解释引力微透镜事件的信号，以寻找银河系晕中的大质量致密晕天体（MACHO）。如果晕暗物质的很大一部分是由MACHO组成的，那么监测程序应该会发现比已知恒星群产生的更多的微透镜事件。在过去的15年中，已经发现了2500多个微透镜事件。目前的发现率大约是每年600个，随着新的监测计划开始，发现率将很快增加。大多数光变曲线是标准的点光源、点透镜类型。这些“香草”光变曲线是高度退化的：在没有清晰视差效应的情况下，只能估计透镜的质量、速度和位置的组合。因此，为了确定与互助人道主义组织有关的贡献，必须依靠统计研究。虽然第一代监测程序的结果限制了H2O的分数，但结果仍然是高度不确定的。另一方面，二元透镜光变曲线包含更多的信息。在理想的情况下，可以测量透镜的位置、速度和质量，并可以对双星的轨道间隔和质量比进行限制。因此，二元透镜可以提供强大的诊断。那些位于源星系中的物质可以被识别出来，并从光环中暗物质的特征中适当地减去。二元MACHO（如果它们存在的话）可以被识别，二元透镜光变曲线中编码的丰富信息展示了测量单个MACHO性质的令人兴奋的前景。通过研究单个事件获得的功率被放大到二元透镜光变曲线的集合。这是因为光变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，同时也探索了二元性质在透镜群体中的分布。在这里，Di Stefano博士和合作者将开发必要的工具，以便系统地发现和解释过去，现在和未来监测计划收集的数据中的二元透镜事件。通过将这项工作应用于几个小组收集的数据，已知的二元透镜事件的数量可能会增加一倍。最重要的是，这些方法将适用于所有其他监测计划的数据，包括宽视场调查，全景巡天望远镜快速反应系统（Pan-STARRS）和大型天气巡天望远镜（LSST）。这项工作还将解决图像变化的自动检测和分类问题，这具有广泛的应用，例如，生物学研究生和本科生将在工作的每个阶段发挥重要作用。迪·斯特凡诺博士还参与了与剑桥公立学校的一个外展计划，其中包括与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.