Initial Configurations
The NSNSs are constructed in quasicircular orbit with compactness of $M/R = 0.336$. We employ the ALF2cc EoS which is based on the ALF2 EoS with the region of rest-mass density $\rho_0\geq\rho_{0s}$ being replaced by $P = \sigma(\rho - \rho_s) + P_s$. Here $\sigma$ is a dimensionless parameter, $\rho$ is the total mass-energy density, and $P_s$ is the pressure at $\rho_s$. The solutions presented in this work assume $\sigma=1.0$, i.e. a causal core, which represents the maximally compact, compressible equation of state. The total ADM mass of the system is $M = 7.90M_\odot$ with each neutron star having a rest mass of $M_0 = 5.18M_\odot$. The orbital angular velocity is $\Omega M = 0.0460$, the coordinate separation is $80.6$ km, and the radius of each neutron star is $10$ km. The NSs are irrotational.
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 Fig. 1: Rest-mass density profile across the x-axis for the NSNS system with the ALF2cc EoS. Horizontal red line corresponds to nuclear density $\rho_{0\rm nuc}$. The insert shows a blow-up near the surface, where the density drops from $\rho_{0\rm nuc}$ to zero in a steep manner. |
The BHBHs are constructed in quasicircular orbit as nonspinning puncture BHs. The total ADM mass of the system, orbital angular velocity, and coordinate separation are the same as the NSNS system.
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