WoU-MMA: Targeted Search for Binary Mergers with Multiple Harmonics in Gravitational Wave Data

WoU-MMA：引力波数据中多重谐波二元合并的定向搜索

• 批准号: 2309360
• 负责人: Tejaswi Nerella
• 金额: $ 30万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-05-01 至 2026-04-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2309360&HistoricalAwards=false
• 关键词: WoU; MMA; Targeted; Search; Binary

Black holes and neutron stars are some of the final endpoints of stars that we see in the universe. These massive and dense compact objects are hard to detect by their electromagnetic emission. Since 2016, interferometric detectors such as LIGO, VIRGO, and KAGRA have helped detect compact objects through the gravitational waves that they emit as they merge with each other. As the detectors' sensitivity improved, the field has moved from the era of notable single detections to one in which we can systematically survey the population of compact objects in the universe. The most interesting and informative detections are those that show complexity (such as overtones and modulations) in the signal, as these effects ultimately inform us about the environment these binaries were assembled in; existing searches do not account for these effects as they complicate the search algorithms. This research program will boost the sensitivity of searches to such signals, and hence extend the reach in the most interesting parts of parameter space - the highest mass mergers (extending all the way to several hundred solar masses), and binaries with very high mass ratios and misaligned spins. Detecting and characterizing these special systems can answer a range of fundamental astrophysical questions, such as the link between stellar-mass black holes and the more massive ones at the centers of galaxies, the endpoint of stellar evolution for the most massive stars (which collapse to the most massive black holes), and the means by which black hole binaries are assembled (from the configurations and sizes of the component spins). In a broader sense, the research program will also facilitate NSF’s long-term vision of building an outside community around the LIGO strain data, introduce fresh perspectives to the analyses, and maximize the potential of pre-existing open data: this will be realized by means of a workshop for the field, and collaborations with local researchers and established university programs to disseminate ideas among high school students.The research is motivated by the presence of subtle effects such as higher harmonics and general-relativistic precession in the loudest individual signals, as well as tentative trends in the astrophysical population, that have already been detected. These events were found by search pipelines that made simplifying assumptions about the signals, i.e., included only a subset of the relevant physical effects; the most important assumption being that the sources are quasi-circular binaries with component spins that are aligned with the orbital angular momentum, and that the waveform is composed of a single harmonic. The aim is to develop a new search that incorporates the effects of higher harmonics, and possibly even precession, and hence is sensitive to a wider range of signals. This will require revisiting all search algorithms in order to achieve the increased sensitivity without paying too large a computational price. The main tasks are to (a) organize templates to account for the diversity in the space of signals, while still retaining the ability to maximize over several geometric parameters, which will control the template bank’s size, and (b) devise methods of optimally combining the individual harmonics, as well as data from multiple detectors. This step is crucial to do correctly to avoid losing sensitivity to existing signals due to enlarging the search space. The methods build on existing full-physics waveform models that are routinely used for parameter inference, and insights from previous searches that used simplified waveform models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

黑洞和中子星是我们在宇宙中看到的恒星的最终端点。这些巨大而致密的物体很难通过它们的电磁发射来探测到。自2016年以来，LIGO、VIRGO和KAGRA等干涉测量探测器通过引力波帮助探测紧凑物体，这些物体在相互融合时发出引力波。随着探测器灵敏度的提高，该领域已经从引人注目的单个探测时代进入了一个我们可以系统地调查宇宙中致密物体的时代。最有趣和最有信息量的检测是那些显示信号复杂性（如泛音和调制）的检测，因为这些影响最终告诉我们这些二进制组合的环境；现有的搜索并没有考虑到这些影响，因为它们使搜索算法复杂化。这个研究项目将提高搜索这些信号的灵敏度，从而扩大对参数空间中最有趣的部分的研究范围——最高质量的合并（一直延伸到几百个太阳质量），以及具有非常高质量比和不对准自旋的双星。探测和描述这些特殊系统可以回答一系列基本的天体物理学问题，例如恒星质量黑洞与星系中心更大质量黑洞之间的联系，最大质量恒星（坍缩成最大质量黑洞）的恒星演化终点，以及黑洞双星组合的方式（从组件旋转的配置和大小）。从更广泛的意义上讲，该研究项目还将促进NSF围绕LIGO应变数据建立一个外部社区的长期愿景，为分析引入新的视角，并最大限度地发挥现有开放数据的潜力：这将通过该领域的研讨会、与当地研究人员和已建立的大学项目合作来实现，以在高中生中传播思想。这项研究的动机是存在一些微妙的影响，比如在最响亮的单个信号中出现更高的谐波和广义相对论进动，以及已经被探测到的天体物理种群的初步趋势。这些事件是通过对信号进行简化假设的搜索管道发现的，即只包括相关物理效应的一个子集；最重要的假设是，源是准圆形双星，其分量自旋与轨道角动量对齐，并且波形由单一谐波组成。其目的是开发一种新的搜索方法，将高次谐波的影响，甚至可能是进动的影响结合起来，从而对更大范围的信号敏感。这将需要重新访问所有搜索算法，以便在不付出太大计算代价的情况下获得更高的灵敏度。主要任务是(a)组织模板以考虑信号空间的多样性，同时仍然保留在几个几何参数上最大化的能力，这将控制模板库的大小，以及(b)设计最佳组合单个谐波的方法，以及来自多个检测器的数据。为了避免由于扩大搜索空间而失去对现有信号的灵敏度，正确地执行这一步至关重要。这些方法建立在现有的全物理波形模型的基础上，这些模型通常用于参数推断，并从以前使用简化波形模型的搜索中获得见解。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。