Binary neutron stars with high compactness and spin

Over the past few years we have developed a formalism to construct binary neutron star initial data with in principle arbitrary masses, spins and eccentricities. However, in practical implementations it has been hard to achieve highly compact, or highly spinning stars. Here we discuss several improvements that allow us to construct initial data also in these cases, so that we now can cover the entire parameter space. When we construct such initial data one has to specify parameters such as a rotation parameter for each star. In order to compare with other calculations or measurements one would like to relate these parameters to more physical quantities such as spin. To facilitate this, we introduce simple estimates for the spin, momentum, mass and center of mass of each individual star. We also show some results from evolutions of highly compact stars.