The gravitational wave background from neutron star birth throughout the cosmos

We present calculations of the stochastic gravitational wave (GW) background resulting from neutron star birth throughout the Universe. We update previous calculations by employing three GW waveforms from Dimmelmeier, Font & Müller, based on three models incorporating general relativistic effects for the axisymmetric core collapse of rotating massive stars. Source‐rate evolution is accounted for by using a simulated star formation rate model based on a ‘flat‐Λ’ cosmology given by Hernquist & Springel. 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 with 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 that it consists predominantly of ‘regular’ and ‘rapid’ core‐collapse models. We note that the background may be considerably enhanced 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.