Magnetosphere Structures and Electromagnetic Precursors of Inspiraling Binary Neutron Stars

Binary neutron star mergers are extraordinary events that can lead to the unveiling of the extreme properties of and physical processes near these compact stars. Electromagnetic and gravitational wave observations of these events can provide constraints on the equation of state models and emission theories while they can test gravity in strong field regimes. Precursor electromagnetic emission can give additional information on the merger dynamics and guide follow up observations and strategies in a variety of bands. However, these emissions are fueled by the dynamic interaction of the inspiraling stars’ magnetospheres. Understanding the patterns and characteristics of these pre-merger emissions requires a comprehensive exploration of the magnetospheres’ global electromagnetic field structure, an element which is also crucial for the understanding of observed phenomena such as Gamma-Ray Bursts, and radio emissions. In this context, we thoroughly explore the multidimensional parameter space that involves the relative strength and direction of the dipole moments, their direction relative to the orbital axis, and the star spin periods relative to the orbital period. In our study, we simulate the magnetosphere of pre-merging neutron star systems using numerical force-free and dissipative MHD simulations and we report Poynting flux and high-energy emission patterns and discuss intriguing examples. Our study explores whether the anisotropic interaction of the Poynting flux with the local environment could lead to distinct electromagnetic signals that influence the GRB afterglow, providing a deeper understanding of the dynamics in these astronomical events.