Forecasting Strongly Lensed Binary Black Hole Rates from the Stochastic Gravitational-Wave Background with TianQin
Abstract
The millihertz stochastic gravitational-wave background (SGWB) provides a population-level probe of stellar-mass binary black holes (BBHs) and their cosmic merger history. We develop a framework using TianQin alone to propagate SGWB-informed BBH population constraints into forecasts of strongly lensed BBH mergers detectable by ground-based gravitational-wave detectors. The framework distinguishes between lensed events with at least one detected image and lens systems in which both images are detected and successfully associated. Using a one-year mock observation, we infer the BBH population and propagate the resulting posterior through a galaxy-scale lensing model with image-level selection. For the adopted system-magnification threshold, μsys≥ 2, the median predicted rate of lensed events with at least one detected image is Reventdet=5.50×10−4 yr−1, while the median rate of associated two-image lens systems is Rsysdet=2.54×10−4 yr−1; the median detectable system fraction is ℱsysdet=3.35×10−4. Compared with the prior-only propagation, the pooled 16th--84th percentile widths decrease by 6.5\% for the event rate, 6.4\% for the system rate, and 4.0\% for the system fraction. Our work establishes a quantitative link between millihertz SGWB inference and forecasts of strongly lensed BBH mergers for ground-based gravitational-wave observations.
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BibTeX
@misc{liang2026forecasting,
title = {{Forecasting Strongly Lensed Binary Black Hole Rates from the Stochastic Gravitational-Wave Background with TianQin}},
author = {Zheng-Cheng Liang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.33751},
eprint = {2610.33751},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.33751},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Forecasting Strongly Lensed Binary Black Hole Rates from the Stochastic Gravitational-Wave Background with TianQin
AU - Zheng-Cheng Liang
PY - 2026
DA - 2026/10/24
PB - arXiv
DO - 10.48550/arxiv.2610.33751
UR - https://arxiv.org/abs/2610.33751
AB - The millihertz stochastic gravitational-wave background (SGWB) provides a population-level probe of stellar-mass binary black holes (BBHs) and their cosmic merger history. We develop a framework using TianQin alone to propagate SGWB-informed BBH population constraints into forecasts of strongly lensed BBH mergers detectable by ground-based gravitational-wave detectors. The framework distinguishes between lensed events with at least one detected image and lens systems in which both images are detected and successfully associated. Using a one-year mock observation, we infer the BBH population and propagate the resulting posterior through a galaxy-scale lensing model with image-level selection. For the adopted system-magnification threshold, μ_sys≥ 2, the median predicted rate of lensed events with at least one detected image is R_event^det=5.50×10^−4 yr^−1, while the median rate of associated two-image lens systems is R_sys^det=2.54×10^−4 yr^−1; the median detectable system fraction is ℱ_sys^det=3.35×10^−4. Compared with the prior-only propagation, the pooled 16th--84th percentile widths decrease by 6.5\% for the event rate, 6.4\% for the system rate, and 4.0\% for the system fraction. Our work establishes a quantitative link between millihertz SGWB inference and forecasts of strongly lensed BBH mergers for ground-based gravitational-wave observations.
ER -