General Relativistic Irrotational Binary Neutron Stars in Quasi-Equilibrium Circular Orbits

Ground based laser interferometric detectors such as LIGO/VIRGO/GEO will begin operation within a few years ¹ and a smaller prototype detector TAMA has started data taking in the year 2000 ^2,3. One of the most promising source of gravitational wave for these detectors is the inspiraling to merger phase of binary neutron stars ⁴. At the last ~ 10 - 100 cycles of the inspiraling phase, the orbital velocity v is still much smaller than the speed of light c (v/c ≪ 1), and the binary evolves in quasi-equilibrium circular orbit in adiabatic manner. However, neutron star radius R becomes comparable to the binary separation a (a/R ~ 2 - 5), that is, the finite size effect is not negligible. In this phase, the binary neutron stars have to be treated numerically taking into account effects of the finite size, tidal deformation and hydrodynamic interaction...