GALACTIC BINARY GRAVITATIONAL-WAVE NOISE WITHIN THE LISA FREQUENCY BAND

Gravitation wave noise associated with unresolved binary stars in the Galaxy is studied with the special aim of determining the upper freque ncy at which it stops contributing to the rms noise level of the propo sed space-borne interferometer (LISA). The upper limit to this backgro und is derived from the statistics of SN Ia explosions, some of which can be triggered by binary white dwarf coalescences. The upper limitin g frequency at which binary stochastic noise crosses LISA rms sensitiv ity is found to lie within the range approximate to 0.03-0.07 Hz, depe nding on the Galactic binary white dwarf coalescence rate. To be relia bly detectable by LISA the energy density of the relic cosmological ba ckground per logarithmic frequency interval should be Omega(GW)h(100)( 2) > 10(-8) at f > 0.03 Hz.