Revisiting stochastic gravitational wave background in the strong signal case

Abstract

Weak-signal limit is often used in estimating stochastic gravitational-wave background (SGWB) intensities. This approximation fails and the signal-to-noise ratio (SNR) can be much weaker when background signals are loud compared to the detector noise. In this work, we find that this issue is especially significant when dealing with networks of detectors that are widely separated. For the TianQin + LISA network, the SNR estimated under the weak-signal limit might be off by as large as an order of magnitude. Contour plots of SNR over the parameter spaces are also presented to indicate regions that will be affected by this correction. Our results suggest that DA and DB type extragalactic double white dwarfs may yield an SGWB with SNR surpassing 100 after 1 year of operation in weak-signal limit scenario, with a redshift-independent merger rate of about 500Mpc−3Myr−1. In fact, this value falls significantly below the necessary threshold. Similar influences arise for first-order phase transitions, yet pinning down the detectable parameters remains formidable due to model uncertainties.

Keywords

• Gravitational-wave
• Space-borne GW detector
• Stochastic gravitational-wave background
• Signal-to-noise ratio
• Weak-signal limit