Enabling Multi-Messenger Astrophysics with Advanced LIGO: from Detector Characterization to Interpretation of Gravitational-Wave Signals

The first observation of gravitational waves in 2015 was a giant leap forward in the history of science, advancing our knowledge of fundamental physics as well as our understanding of the structure and origin of the universe. Additionally, the new branch of science now known as gravitational-wave astronomy has helped maintain the United States' leading role in science and technology and sustain the growth of a talented homegrown workforce in these disciplines, both of which are critical to the nation's success. The success of gravitational-wave astronomy has been demonstrated through the confirmation of previously untested scientific predictions, such as Hawking's black hole area law and the origin of heavy elements in the periodic table, as well as through extraordinarily precise measurements of some of the fundamental laws of nature, including Einstein's theory of general relativity. Yet, a great deal of the underlying physics of gravitational-wave sources remains elusive and requires further investigation to unveil the full wealth of information encoded in the signals from these cosmic emitters and to further probe our understanding of the fundamental forces of nature. In this context, this project supports the core mission of the nascent International Gravitational-Wave Network consortium through scientific operations and research and development activities in detector science and data analysis, aimed at advancing our knowledge at the frontier of high-energy astrophysics and cosmology. The project also integrates research and educational activities that promote science and technology among diverse segments of the state and U.S. population, including school students and the general public, thus increasing awareness of U.S. scientific achievements and of the supporting role of the National Science Foundation. Specific scientific operations under this award include conducting astrophysical searches for gravitational-wave sources in conjunction with multi-messenger observations, such as searches for gravitational-wave signals triggered by optical supernovae and gamma-ray bursts; improving data analysis algorithms currently used by the gravitational-wave community to search for these signals; and characterizing the performance of the U.S.-based LIGO detectors within the broader international scientific effort. Research and development activities include enhancing detector efficiency through the use of artificial intelligence-based methods for gravitational-wave data characterization, including the development of machine learning tools for data quality investigations and detector noise mitigation, as well as improvements to gravitational-wave searches in future observing campaigns. These efforts include designing advanced machine learning algorithms to increase the chances of gravitational-wave detections in multi-messenger searches and building a framework to improve the significance of upper limits in the absence of detections. Together, these activities enable gravitational-wave detectors to operate effectively and continue producing transformative science while increasing the amount of physical information that can be extracted from the data. 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.