Collaborative research: NSF-BSF: WOU-MMA: RUI: from meters to parsecs, from milliseconds to years: a journey through space and time with binary mergers

The National Science Foundation's Mathematical and Physical Sciences program (CFDA 47.049) awarded $366,329 to California State University, Sacramento (via University Enterprises, Inc.) on September 1, 2025, for a collaborative research project with Purdue University and Northwestern University, in partnership with Israeli institutions. This three-year project (through August 31, 2028) will develop comprehensive numerical simulations and computational models of binary neutron star and neutron star-black hole mergers across multiple spatial and temporal scales. The research will directly connect pre-merger binary states to post-merger electromagnetic emission regions, enabling researchers to generate consistent jet profile models, interpret multi-wavelength counterparts of gravitational wave events, and distinguish between black hole and neutron star compact remnants powering short gamma-ray bursts.

The project will deliver physics-based models and emission predictions that advance fundamental understanding of general relativity, compact objects, neutron star equation of state, plasma physics, and nucleosynthesis from merger events. Additionally, the award emphasizes workforce development and K-12 STEM education as core broader impacts, positioning the collaborative research effort to contribute to both scientific discovery and educational advancement in the mathematical and physical sciences.

Abstract

Mergers of ultra-compact stellar remnants called neutron STARS have now been observed. They provide new tools to study general relativity, compact objects, neutron star equation of state, plasma physics, astrophysical jet physics, and nucleosynthesis. A joint US-israeli research team will develop numerical simulations of binary mergers through their full development. The US effort is jointly led by california state university, sacramento, purdue university, and northwestern university. The team will aim to construct ?meter-to-parsec? Models of binary mergers, which follow through the entire journey of length and time scale, by directly connecting the pre-merger state of a neutron star - neutron star (NS-NS) or neutron star - black hole (NS-BH) binary to the regions where the observed photons are produced. This project has two main broader societal impacts : (i) development of a globally competitive stem workforce; and (II) improvement of stem education of k-12 students. The models will allow interpretation of various observables of the system by connecting them with the conditions inside the ejecta and in the pre-merger phase: (i) generating consistent models of the jet profile will allow the researchers to connect the observed off-axis emission to the conditions at the base of the jet and help construct reliable emission models for the multi-wavelength counterparts of gravitational wave events. (II) to date, IT is still not known if the compact merger remnants powering short gamma-RAY bursts (sgrb) jets are BHS or NSS. By mapping the main differences between the physical properties and emission profiles of jets powered by these two types of engines, the research will provide a method to distinguish between them, independent of the kilonova emission, which may not be detectable in typical multi-messenger events. (III) the question of energy composition in the jet at large scales is a long standing puzzle in sgrbs. The answer can shed light on the acceleration mechanisms and emission processes responsible for the prompt gamma-rays. In addition, the sacramento state principal investigator (PI) will partner with the sacramento state planetarium to develop a new curriculum for k-5 audiences that visit the planetarium as part of their free school field trips. The purdue PI will partner with the saturday morning astrophysics purdue program for middle and high-school students to develop and lead an annual session on the detection of gravitational waves and the study of compact objects in the universe. The northwestern PI will partner with the reach high school program to mentor chicago-area high school students each summer. 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.- subawards are planned for this award.