Demagnified GWs from Cosmological Double Neutron Stars and GW Foreground Cleaning Around 1Hz

TL;DR

This paper examines how gravitational lensing can demagnify gravitational waves from distant neutron star binaries, potentially creating a foreground that could interfere with primordial GW detection, but finds this effect is likely manageable with future detectors.

Contribution

It introduces a simple lensing model to evaluate the impact of demagnified GW signals on foreground contamination in future GW observations.

Findings

Residual foreground below detection threshold Omega_{GW} ~ 10^{-16} for BBO/DECIGO

Demagnified signals can form a GW foreground that may affect primordial GW detection

Lensing effects are manageable with current models and future detectors

Abstract

Gravitational waves from cosmological double neutron star binaries can be significantly demagnified by strong gravitational lensing effect, and the proposed future missions such as BBO or DECIGO might miss some of the demagnified GW signals below a detection threshold. The undetectable binaries would form a GW foreground which might hamper detection of a very weak primordial GW signal. We discuss the outlook of this potential problem, using a simple model based on the singular-isothermal-sphere lens profile. Fortunately, it is expected that, for presumable merger rate of NS+NSs, the residual foreground would be below the detection limit Omega_{GW} ~ 10^{-16} realized with BBO/DECIGO by correlation analysis.