Exascale Simulations of Compact Binary Mergers

Compact binary mergers relate to some of the most pressing open problems in astrophysics, including the nature of gravity and matter under extreme conditions, the astrophysical site of heavy-element production, and the mechanism that powers gamma-ray bursts. LIGO undergoes a series of upgrades that double its sensitivity and, in 2027, begins its fifth observing run (O5). LIGO operates alongside Virgo in Italy and KAGRA in Japan, forming an international network of detectors. Extensive electromagnetic follow-up observations take place with the Vera C. Rubin Observatory, the Nancy Grace Roman Space Telescope, and the James Webb Space Telescope. The combined gravitational-wave and electromagnetic data encode answers to key questions in high-energy and nuclear astrophysics.

This project performs large-scale compact binary merger simulations to unlock that information. The team conducts general-relativistic hydrodynamics simulations of tidally interacting neutron stars at very high resolution over more than 20 orbits to develop new gravitational-wave data analysis pipelines. These simulations address systematic uncertainties in current models, which otherwise dominate over statistical uncertainties for the high signal-to-noise events expected in O5. The team also carries out general-relativistic global magnetohydrodynamics simulations of merging neutron stars at unprecedented resolution to study turbulence and dynamo action driven by the magnetorotational instability in the remnant. These simulations quantify the impact of turbulent-viscous torques on the post-merger gravitational-wave signal and assess the viability of massive neutron star remnants as engines for gamma-ray bursts and kilonovae.