Gravitational Wave Physics and Astronomy

随着引力波的探测，我们开始在天文学和天体物理学的编年史上、在我们对引力的实验理解以及我们对宇宙的知识上写下新的篇章。该奖项资助工具和技术的开发，这些工具和技术的使用可以提高一类重要的引力波探测器的效率和科学回报，称为脉冲星定时阵列。通过脉冲星定时阵列探测引力波涉及到对来自特定类型天文物体--脉冲星--的许多不同例子的无线电信号进行多年的准确和精确监测。通过脉冲星计时探测引力波是一种机会主义的做法：我们只有大自然提供的那些脉冲星才能提供给我们。脉冲星定时阵列对引力波的灵敏度取决于能够以足够的准确度和精确度监测的脉冲星的数量，以及天空中不同脉冲星的相对方向。可用于监测脉冲星的资源是有限的；此外，专门用于每颗脉冲星的计时的可用资源可显著影响监测的准确性和精确度。通过适当地选择被监测的脉冲星和监测每个脉冲星所花费的时间，脉冲星定时阵列的灵敏度可以最大化，从而导致更快地第一次探测引力波，并从这一努力中获得更有信息量的科学产品。脉冲星定时阵列(PTA)是唯一可以探测到与真正超大质量(大约10亿个太阳质量或更多太阳质量)黑洞双星有关的引力波的方法，这些双星与许多星系的合并有关。对这些双星的观察将为早期宇宙结构的形成和今天观察到的星系的演化提供重要线索。PTA的灵敏度取决于与每个脉冲星有关的计时噪声、脉冲星-地球视线方向在阵列中的分布、确定脉冲到达时间的节奏(即，阵列脉冲星是否每六周计时一次？一个月一次？每周一次？)，以及每次观测在脉冲星上花费的时间(例如，30分钟？一小时？几个小时？)。该项目开发了一套量化指标，可用于“调整”脉冲星计时阵列，以最大限度地提高其科学回报，其特点是三种不同的衡量标准--最快探测、最佳多信使天文学前景和引力波源的最佳特征--并应用这些衡量标准，以确定与用于引力波探测的脉冲星计时相关的当前观测时间分配的变化可以带来什么好处。

With the detection of gravitational waves we are beginning to write a new chapter in the annals of astronomy and astrophysics, our experimental understanding of gravity, and our knowledge of the cosmos. This award funds the development of tools and techniques whose use can improve the efficiency and science-return of an important class of gravitational wave detectors, referred to as pulsar timing arrays. Gravitational wave detection via a pulsar timing array involves the accurate and precise monitoring of the radio signals from many different examples of a particular type of astronomical object - pulsars - over periods of many years. Gravitational wave detection via pulsar timing is opportunistic: we have available to us only those pulsars that Nature has provided. The sensitivity of a pulsar timing array to gravitational waves depends on the number of pulsars that can be monitored with sufficient accuracy and precision, and the relative direction of the different pulsars on the sky. The resources available to monitor the pulsars are limited; additionally, the available resources devoted to the timing of each pulsar can influence significantly the accuracy and precision with which it can be monitored. By appropriately choosing the pulsars that are monitored and the time spent monitoring each the sensitivity of the pulsar timing array can be maximized, leading to more rapid first detection of gravitational waves and a more informative scientific product from the effort. Pulsar timing arrays (PTAs) are the only means by which the gravitational waves associated with truly supermassive (on order of a billion or more solar masses) black hole binaries, which are associated with the merger of many galaxies, can be detected. Observation of these binaries will provide important clues to the formation of structure in the early universe and the evolution of the galaxies that are observed today. The sensitivity of a PTA depends on the timing noise associated with each pulsar, the distribution of pulsar-Earth line-of-sight directions in the array, the cadence with which pulse arrival times are determined (i.e., is an array pulsar timed once every six weeks? once a month? once a week?), and the observing time spent on the pulsar at each observation (e.g., 30 min? an hour? several hours?). This project develops a set of quantitative metrics that can be used to "tune" a pulsar timing array to maximize its science return as characterized by three different measures - quickest detection, best multi-messenger astronomy prospects, and best characterization of gravitational wave source - and applies these metrics to identify what benefits can come from a change in the present observing time allocations associated with pulsar timing for gravitational wave detection.