Study Projects Thousands of Strongly Lensed Gravitational Waves Detectable by Future Space Observatories
Researchers have developed a simulation framework to predict how many gravitational wave events detected by future space-borne detectors like LISA and DECIGO may be strongly lensed by intervening galaxies or galaxy clusters. For a four-year LISA mission, the expected number of lensed events ranges from 0 to 131 depending on the assumed formation model for massive black hole binaries, while DECIGO could detect 0 to 44 lensed events in one year. The findings highlight that overlapping lensed signals will be a common complication in space-based gravitational wave astronomy, affecting both signal detection and event identification.
A new preprint posted to arXiv presents a comprehensive framework — dubbed GW-LMC-Space — for constructing mock catalogs of strongly lensed gravitational wave (GW) events expected to be observed by future space-borne detectors, specifically LISA and DECIGO. Using realistic astrophysical models for both GW source populations and the distribution of gravitational lenses such as galaxies and galaxy clusters, the authors estimate that LISA could detect between 0 and 131 lensed events over four years, with the wide range reflecting uncertainty in massive black hole binary (MHBH) formation models and a peak lensing probability of roughly 0.3%. For DECIGO, the projected yield is 0 to 44 lensed events per year across stellar-mass binary black holes, binary neutron stars, and neutron star–black hole binaries, with a lensing probability of approximately 0.15%. A key finding is that signal overlap — where multiple lensed GW signals arrive within the same detection window — is expected to be a frequent occurrence in space-based detectors, complicating both signal-to-noise ratio estimation and the identification of individual events. The authors argue that analysis pipelines for future missions must explicitly account for this overlap effect to correctly interpret lensed GW observations.
What's missing
The study is a theoretical simulation framework and has not been validated against real lensed GW detections, which do not yet exist for space-borne detectors. Key limitations include the large model-dependent uncertainty in MHBH formation rates and the fact that LISA and DECIGO have not yet launched, meaning detector sensitivity curves used are based on projected specifications. The framework's ability to handle more complex lens configurations (e.g., substructure, line-of-sight halos) and its treatment of waveform systematics under signal overlap remain open questions.
What different sources said
- arXiv astro-phCenter
Detectability to extreme mass ratio inspirals with alternative space-based detector networks
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