The gravitational wave background from neutron star birth throughout the cosmos

Abstract

We present calculations of the stochastic gravitational wave (GW) background result- ing from neutron star birth throughout the Universe. We update previous calculations by employing three GW waveforms from Dimmelmeier, Font & Muller (2002), based on three models incorporating general relativistic eects for the axisymmetric core col- lapse of rotating massive stars. Source-rate evolution is accounted for by using a sim- ulated star formation rate model based on a 'flat-⁄' cosmology (Hernquist & Springle 2003). We show that the GW background is only weakly dependent on the source-rate evolution model. Prominent features in the single-source GW spectral strain can be related to the calculated background spectra, even though the features are broadened and redshifted because of contributions from high-redshift sources. The background spectral closure density is reduced by 1-2 orders of magnitude compared to previous calculations, a consequence of using relativistic single-source GW waveforms and a more slowly evolving source-rate density. Duty cycle estimates for this background imply a non-continuous signal, assuming it consists predominantly of 'regular' and 'rapid' core-collapse models. We note that the background may be considerably en- hanced by the inclusion of dynamic post-collapse instabilities (bar-modes), which are not included in this work, so our estimates for this background may be lower limits.