We present the first computations of quasiequilibrium binary neutron stars with different mass components in general relativity , within the Isenberg-Wilson-Mathews approximation .
We consider both cases of synchronized rotation and irrotational motion .
A polytropic equation of state is used with the adiabatic index \gamma = 2 .
The computations have been performed for the following combinations of stars : ( M / R ) _ { \infty, ~ { } star~ { } 1 } vs . ( M / R ) _ { \infty, ~ { } star~ { } 2 } = 0.12 ~ { } { vs . } ~ { } ( 0.12 ,~ { } 0.13 ,~ { } 0.14 ) ,~ { } 0.1 % 4 ~ { } { vs . } ~ { } ( 0.14 ,~ { } 0.15 ,~ { } 0.16 ) ,~ { } 0.16 ~ { } { vs . } ~ { } ( 0.16 ,~ { } 0.17 ,~ { } % 0.18 ) ,~ { } { and } ~ { } 0.18 ~ { } { vs . } ~ { } 0.18 , where ( M / R ) _ { \infty } denotes the compactness parameter of infinitely separated stars of the same baryon number .
It is found that for identical mass binary systems there is no turning point of the binding energy ( ADM mass ) before the end point of the sequence ( mass shedding point ) in the irrotational case , while there is one before the end point of the sequence ( contact point ) in the synchronized case .
On the other hand , in the different mass case , the sequence ends by the tidal disruption of the less massive star ( mass shedding point ) .
It is then more difficult to find a turning point in the ADM mass .
Furthermore , we find that the deformation of each star depends mainly on the orbital separation and the mass ratio and very weakly on its compactness .
On the other side , the decrease of the central energy density depends on the compactness of the star and not on that of the companion .