State of the Art Simulations in Binary Neutron Star Mergers

• Grant number: 24/21086-5
• Support Opportunities: Scholarships abroad - Research
• Start date: September 10, 2025
• End date: September 09, 2026
• Field of knowledge: Physical Sciences and Mathematics - Physics
• Agreement: European Research Council
• Principal Investigator: Maximiliano Ujevic Tonino
• Grantee: Maximiliano Ujevic Tonino
• Host Investigator: Tim Dietrich
• Host Institution: Centro de Ciências Naturais e Humanas (CCNH). Universidade Federal do ABC (UFABC). Ministério da Educação (Brasil). Santo André , SP, Brazil
• Institution abroad: University of Potsdam, Germany

Abstract

Multi-messenger studies combining gravitational wave and electromagnetic observations of merging neutron stars are an unprecedented tool to study extreme astrophysical phenomena and, with it, unveil key features about the nature of matter and spacetime. In this context, a topic of active research, both on the experimental and theoretical fronts, is that of binary neutron stars (BNS) mergers, which are prominent sources of multi- messenger signals. The main goal of such studies is to shed light on the structure of neutron stars and their underlying physics. Despite the continuous effort put on this subject, many details are still plagued by uncertainties which may be better reduced with increasingly realistic modelling of BNS systems, whose results are fundamental for a correct interpretation of observational data. Hence, this project focuses on theoretically approaching BNSs via numerical simulations of the late-inspiral, merger and post-merger stages using Numerical Relativity (NR). In particular, we want to address key aspects that are still missing together in state of the art methods: (i) the description of muons within the neutron stars (NSs) and their role with respect to weak-force interactions that may occur during a BNS merger by describing them using the first-order multipolar transport scheme; and (ii) the incorporation of resistive general relativistic magnetohydrodynamics (GRMHD) which is usually avoided due to the complexity of the evolution equations. Such an endeavor is of great importance not only because muons and magnetic fields are expected to be found within NSs and NS collisions, but also because their presence may significantly alter the fate of a BNS dynamical evolution through their participation in very energetic nuclear reactions. Therefore, the aim of this project is to upgrade the code infrastructure of our NR code BAM to include the mentioned key aspects. We intend to perform the first BNS simulations that include these upgrades and investigate their roles in BNS mergers by analyzing imprints on the emitted gravitational waves (GWs), the powered kilonovae, the gamma ray burst (GRB) afterglow, and nucleosynthesis reactions.