Search for a stochastic gravitational-wave background using a global interferometer network
Observing the gravitational-wave background (GWB) with Earth-based interferometric detectors will provide insights into astrophysical and cosmological processes in the early Universe. To confidently claim a detection in the future, a profound knowledge of the data quality and potential contamination by noise sources is of utmost importance. In this work a comprehensive study is presented on a wide variety of data quality issues that may arise in the search for an isotropic GWB with current and next generation Earth-based gravitational-wave (GW) interferometric detectors. First of all, spectral artefacts are addressed during the third observing run by LIGO and Virgo. Secondly, one needs to understand the effect of noise sources which are correlated between the observing detectors. When not properly accounted for, these noise sources could bias future detections of a GWB in the Hz to kHz frequency band. Observations of Earth-scale correlations in magnetic field fluctuations are described between 1Hz and 1kHz. By using measurements of the coupling strength of magnetic fields to GW detectors, the effect of correlated magnetic noise on GW searches is predicted. Searches for an isotropic GWB could become contaminated by correlated magnetic noise when the detectors reach their design sensitivity in the second half of the 2020 decade. Future projects such as the Einstein Telescope (ET) and Cosmic Explorer, should seriously consider the threat of magnetic noise. If not addressed, environmental magnetic noise will dominate the detectors' sensitivity below ~15Hz. The equilateral triangular configuration of three nested GW detectors of the ET brings certain advantages such as the sky-position-independent null channel, which is insensitive to GW signals from any direction. This would prove useful for the estimation of the detector noise, as the ET will have many overlapping signals at any given time. Within this context, this work includes a description how to take the effect of non-identical and correlated noise sources into account in the null channel framework. However, the triangular detector configuration comes at a cost. The co-located placement of different detectors results in additional noise sources coupling coherently to multiple detectors. This could have a detrimental impact on the ET's capabilities in observing a GWB. Furthermore, the possibility of correlated seismic and Newtonian noise is investigated and shown to be problematic. More specifically, correlated Newtonian noise from seismic body waves has the potential to overwhelm a GWB signal up to ~40Hz by many orders of magnitude.
Antwerp : Universiteit Antwerpen & Université Côte d’Azur , 2023
xvii, 324 p.
Supervisor: Van Remortel, Nick [Supervisor]
Supervisor: Christensen, Nelson [Supervisor]
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Creation 17.10.2023
Last edited 26.10.2023
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