Quasiequilibrium sequences of binary neutron stars are numerically calculated in the framework of the Isenberg-Wilson-Mathews ( IWM ) approximation of general relativity .
The results are presented for both rotation states of synchronized spins and irrotational motion , the latter being considered as the realistic one for binary neutron stars just prior to the merger .
We assume a polytropic equation of state and compute several evolutionary sequences of binary systems composed of different-mass stars as well as identical-mass stars with adiabatic indices \gamma = 2.5 , 2.25 , 2 , and 1.8 .
From our results , we propose as a conjecture that if the turning point of binding energy ( and total angular momentum ) locating the innermost stable circular orbit ( ISCO ) is found in Newtonian gravity for some value of the adiabatic index \gamma _ { 0 } , that of the ADM mass ( and total angular momentum ) should exist in the IWM approximation of general relativity for the same value of the adiabatic index .