Galactic Binary Gravitational Wave Noise within the LISA Frequency Band

Abstract

Gravitation wave noise associated with unresolved binary stars in the Galaxy is studied with the special aim of determining the upper frequency at which it stops contributing to the rms noise level of the proposed space-borne interferometer (LISA). The upper limit to this background is derived from the statistics of SN Ia explosions, some of which can be triggered by binary white dwarf coalescences. The upper limiting frequency at which binary stochastic noise crosses LISA rms sensitivity is found to lie within the range ≈ 0.03-0.07 Hz, depending on the Galactic binary white dwarf coalescence rate. To be reliably detectable by LISA, the energy density of the relic cosmological background per logarithmic frequency interval should be Ω_GW h²₁₀₀ > 10⁻⁸ at f > 0.03 Hz.