Binary Neutron Star Mergers: From Numerical Relativity Simulations to Kilonova Properties

by Roucheng Zhai

Thursday 1 Oct 2026, 09:00 → 11:00 Europe/Berlin

Abbeanum / 4 - HS 4 (TPI, FSU Jena)

Binary neutron star mergers (BNSMs) are among the most energetic events in the universe and a primary site of the r-process that produces heavy elements. Strong general-relativistic effects make numerical simulations necessary to study their properties. In this talk, I will present our first results validating the pipelines and discuss possible extensions for studying kilonova light curves and nucleosynthesis. We use AthenaK, a machine-portable GRMHD code with M1 neutrino transport, on modern GPU clusters. We use widely used equations of state (EOSs): BLh, DD2, SFHo, and SLy4 for equal- and unequal-mass BNSMs to assess how they influence merger outcomes. We find that harder EOSs (BLh and DD2) produce long-lived neutrino-driven winds and ejecta with higher electron fractions, while softer EOSs (BLh and SLy4) produce short-lived remnants that collapse within 10 ms in the equal-mass case. From these simulations, we extract ejecta to compute electromagnetic signals and nucleosynthesis with codes like KNEC, which we used to study composition-mixing effects in BNSM ejecta. This work will precede a project simulating a thousand BNSMs to study their statistical properties, which can help link merger properties to EM observables.