Hybrid equation of state approach in binary neutron-star merger simulations

Understand

We investigate the use of hybrid equations of state in binary neutron-star simulations in full general relativity, where thermal effects are included in an approximate way through the adiabatic index $\Gamma_{\rm{th}}$.

• We employ a newly developed finite-temperature equation of state derived in the Brueckner-Hartree-Fock approach and carry out comparisons with the corresponding hybrid versions of the same equation of state, investigating how different choices of $\Gamma_{\rm{th}}$ affect the gravitational-wave signal and the hydrodynamical properties of the remnant.
• We also perform comparisons with the widely used SFHo equation of state, detailing the differences between the two cases.
• Overall, we determine that when using a hybrid equation of state in binary neutron-star simulations, the value of thermal adiabatic index $\Gamma_{\rm{th}} \approx 1.7$ best approximates the dynamical and thermodynamical behaviour of matter computed using complete, finite-temperature equations of state.