Initial data for high-compactness black hole-neutron star binaries

Understand

For highly compact neutron stars, constructing numerical initial data for black hole-neutron star binary evolutions is very difficult.

• We describe improvements to an earlier method that enable it to handle these more challenging cases.
• We examine the case of a 6:1 mass ratio system in inspiral close to merger, where the star is governed by a polytropic $\Gamma=2$, an SLy, or an LS220 equation of state.
• In particular, we are able to obtain a solution with a realistic LS220 equation of state for a star with compactness 0.26 and mass 1.98 $M_\odot$, which is representative of the highest reliably determined neutron star masses.