Information about the last stages of a binary neutron star inspiral and the final merger can be extracted from quasi-equilibrium configurations and dynamical evolutions .
In this article , we construct quasi-equilibrium configurations for different spins , eccentricities , mass ratios , compactnesses , and equations of state .
For this purpose we employ the SGRID code , which allows us to construct such data in previously inaccessible regions of the parameter space .
In particular , we consider spinning neutron stars in isolation and in binary systems ; we incorporate new methods to produce highly eccentric and eccentricity reduced data ; we present the possibility of computing data for significantly unequal-mass binaries with mass ratios q \simeq 2 ; and we create equal-mass binaries with individual compactness up to \mathcal { C } \simeq 0.23 .
As a proof of principle , we explore the dynamical evolution of three new configurations .
First , we simulate a q = 2.06 mass ratio which is the highest mass ratio for a binary neutron star evolved in numerical relativity to date .
We find that mass transfer from the companion star sets in a few revolutions before merger and a rest mass of \sim 10 ^ { -2 } M _ { \odot } is transferred between the two stars .
This amount of mass accretion corresponds to \sim 10 ^ { 51 } ergs of accretion energy .
This configuration also ejects a large amount of material during merger ( \sim 7.6 \times 10 ^ { -2 } M _ { \odot } ) , imparting a substantial kick to the remnant neutron star .
Second , we simulate the first merger of a precessing binary neutron star .
We present the dominant modes of the gravitational waves for the precessing simulation , where a clear imprint of the precession is visible in the ( 2 , 1 ) mode .
Finally , we quantify the effect of an eccentricity reduction procedure on the gravitational waveform .
The procedure improves the waveform quality and should be employed in future precision studies .
However , one also needs to reduce other errors in the waveforms , notably truncation errors , in order for the improvement due to eccentricity reduction to be effective .