RUI: LIGO Calibration, Gravitational-Wave Searches, and Parameter Estimation in the Advanced Detector Era

2015年9月，先进的LIGO首次直接探测到引力波，正式开启了引力波天文学的时代，将大量新的天体物理学带到我们的家门口。这笔拨款支持凯尼恩学院LIGO科学合作组织成员的工作。凯尼恩LIGO小组成员在校准高级LIGO干涉仪和寻找来自大黑洞的引力波信号方面发挥了主导作用。aLIGO探测器的校准是探测器收集数据后的第一个基本步骤。只有在校准数据之后，才能开始搜索引力波信号。LIGO的科学家们寻找了一系列的来源，但最有希望的来源是两个紧密的天体物理物体的结合，比如黑洞和中子星。从历史上看，LIGO对质量高达100倍太阳质量的黑洞系统进行了仔细的搜索。凯尼恩LIGO小组的成员正在努力将这种搜索扩展到更高质量的黑洞。这些大黑洞可能提供了星系中心超大质量黑洞是如何形成的关键答案。此外，凯尼恩LIGO小组正在探索和提高aLIGO提取中子星组成物质信息的能力，为首次从合并中子星系统中探测引力波做准备。虽然来自双中子星系统的电磁信号可以提供对中子星表面的洞察，但来自双中子星系统的引力波探测可以更深入地挖掘并揭示虚幻的中子星物质本身的秘密。最后，该项目还支持扩展现有的美国国家科学基金会资助的凯尼恩学院外展项目，该项目旨在通过令人兴奋的实践科学研讨会吸引中学生。在整个学年的几个星期六，分别为中学男生（LADS：学习和做科学）和中学女生（GSS：女生科学星期六）举办讲习班。该奖项支持引力波物理学领域的三项主要工作。第一个问题与正在进行的校准aLIGO探测器的工作有关。具体来说，凯尼恩LIGO小组成员不仅要维护现有的低延迟校准软件，这是一项艰巨的任务，因为校准程序随着干涉仪的升级而不断变化，而且他们还将努力将当前校准软件的延迟从几十秒左右减少到几秒。尽可能低的延迟校准对于引力波候选信号的电磁跟踪至关重要。减少校准软件延迟的主要方法是降低程序的复杂性，将尽可能多的校准程序转移到实时仪器计算机中，以及提高所有现有校准软件的计算效率。该合同还支持中等质量黑洞双星（IMBHB）系统的建模和匹配过滤器搜索的开发和执行。搜索的目标是首次在中等质量范围内对黑洞进行可靠的探测，或者为IMBHB系统的存在提供上限。现有的搜索软件正在进行优化，以适应更大质量的需求，因此波形更短，匹配滤波器搜索，并且正在开发搜索，以便在未来的观测运行中以低延迟模式运行。最后，这笔拨款支持开发工具，从双中子星引力波探测中提取有关中子星状态方程的信息。马尔可夫链蒙特卡罗（MCMC）引力波参数估计软件正在改进，以更优地探索中子星状态方程参数空间，并正在开发允许使用不同模型的中子星状态方程的软件。来自双中子星系统的最初几次引力波探测将能够提供有关中子星物质的丰富新知识。

The first direct detection of gravitational waves by Advanced LIGO in September 2015 has officially launched the era of gravitational-wave astronomy, bringing a plethora of new astrophysics to our doorstep. This grant supports the work of members of the LIGO Scientific Collaboration at Kenyon College. Kenyon LIGO group members have lead roles in the calibration of the Advanced LIGO (aLIGO) interferometers and the search for gravitational wave signals from large black holes. The calibration of the aLIGO detectors is the first fundamental step after data has been collected by the detector. Only after the data is calibrated can searches for gravitational wave signals begin. LIGO scientists search for a range of sources, but the most promising source is the coalescence of two compact, astrophysical objects, such as black holes and neutron stars. Historically, LIGO has performed careful searches for black hole systems with masses that range up to 100 times the mass of the Sun. Members of the Kenyon LIGO group are part of the effort to expand this search to black holes of even higher masses. These large black holes may hold key answers as to how the supermassive black holes at the centers of galaxies were formed. Additionally, the Kenyon LIGO group is exploring and improving aLIGO's ability to extract information about the matter that composes neutron stars in preparation for the first gravitational wave detection from a coalescing neutron star system. While electromagnetic signals from binary neutron star systems can provide insight into the surface of neutron stars, the detection of gravitational waves from a binary neutron star system could dig deeper and reveal secrets of the illusive neutron star matter itself. Finally, this project also supports the expansion of an existing NSF-funded outreach program at Kenyon College that targets engaging middle-school-aged audiences with exciting, hands-on science workshops. Separate workshops are held for middle school boys (LADS: Learning and Doing Science) and middle school girls (GSS: Girls Science Saturdays) several Saturdays throughout the school year. This award supports three main efforts in the field of gravitational-wave physics. The first is related to ongoing work in the calibration of the aLIGO detectors. Specifically, Kenyon LIGO group members will not only maintain existing low-latency calibration software, which is a large task as the calibration procedure is constantly changing with upgrades to the interferometers, but they will also work towards reducing the latency of the current calibration software from around a few tens of seconds down to a few seconds. The lowest possible latency calibration is crucial for electromagnetic follow-up of gravitational wave signal candidates. The main methods that will be employed to reduce the latency of the calibration software are to reduce the complexity of the procedure, shift as much of the calibration procedure as possible into the real-time instrument computers, and improve the computational efficiency of all existing calibration software. The award also supports the development and execution of a modeled, matched-filter search for intermediate mass black hole binary (IMBHB) systems. The goal of the search is to make the first confident detection of black holes in the intermediate mass range or to provide upper limits on the existence of IMBHB systems. Existing search software is being optimized to fit the needs of a higher mass, and therefore shorter waveform, matched filter search, and the search is being developed to run in a low-latency mode during future observing runs. Finally, this grant supports the development of tools to extract information about the neutron star equation of state from a binary neutron star gravitational wave detection. Markov Chain Monte Carlo (MCMC) gravitational wave parameter estimation software is being modified to more optimally explore the neutron star equation of state parameter space, and software to allow for the use of different models of the neutron star equation of state is being developed. The first few gravitational wave detections from binary neutron star systems will be able to provide a wealth of new knowledge about neutron star matter.