CAREER: Theoretical Models of Neutron Star Matter Effects from Inspiral to Post-Merger

Coalescing binary neutron star systems, driven by gravitational-wave emission, provide a rare yet crucial natural laboratory for studying fundamental questions in astrophysics, nuclear physics, and gravitation under extreme conditions. This award supports theoretical research that strengthens the connection between the physical properties of neutron stars and the signals measured by current and next-generation gravitational-wave observatories. By improving the understanding of these observations, it contributes to U.S. leadership in gravitational-wave astronomy. The award also promotes workforce development by providing advanced training to graduate and undergraduate students in analytical modeling, numerical computation, and data analysis. In parallel, partnerships with rural middle school teachers in Montana will broaden access to STEM education, helping to expand the pipeline of future scientists and engineers and supporting economic growth in Montana and across the nation. The research focuses on developing physically grounded gravitational-wave models for binary neutron star systems across their evolution, from early inspiral through post-merger. During the inspiral phase, first-principles theoretical methods will incorporate nonlinear fluid dynamics, spin precession, and orbital eccentricity into relativistic waveform models, enabling more accurate inference of neutron star structure, improved constraints on formation channels, and new tests of general relativity. The work will also extend theoretical modeling into the post-merger regime by constructing a first-principles description of oscillations in the merger remnant, explaining features seen in numerical relativity simulations, and identifying new observables sensitive to dense-matter physics. Together, these advances will enhance the scientific return of gravitational-wave observations and provide essential tools for the analysis of future detections. 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. NSF Award ID: 2541579 | Program: 01002930DB NSF RESEARCH & RELATED ACTIVIT,01003031DB NSF RESEARCH & RELATED ACTIVIT,01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Hang Yu | Institution: Montana State University, BOZEMAN, MT | Award Amount: $205,958 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2541579 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2541579.html