Gravitational waves from binary neutron stars in quasiequilibrium circular
orbits are computed using an approximate method which we propose in this paper.
In the first step of this method, we prepare general relativistic irrotational
binary neutron stars in a quasiequilibrium circular orbit, neglecting
gravitational waves. We adopt the so-called conformal flatness approximation
for a three-metric to obtain the quasiequilibrium states in this paper. In the
second step, we compute gravitational waves, solving linear perturbation
equations in the background spacetime of the quasiequilibrium states. Comparing
numerical results with post Newtonian waveforms and luminosity of gravitational
waves from two point masses in circular orbits, we demonstrate that this method
can produce accurate waveforms and luminosity of gravitational waves. It is
shown that the effects of tidal deformation of neutron stars and strong general
relativistic gravity modify the post Newtonian results for compact binary
neutron stars in close orbits. We indicate that the magnitude of a systematic
error in quasiequilibrium states associated with the conformal flatness
approximation is fairly large for close and compact binary neutron stars.
Several formulations for improving the accuracy of quasiequilibrium states are
proposed.Comment: 26 pages, to be published in PR
