Finding black hole mergers early enough to alert telescopes in time

Catching a black hole merger in gravitational waves while telescopes are already watching requires advance warning — hours to weeks before the event. Testing against the LISA Data Challenge benchmark dataset, both a zero-latency filter and a new inpainting technique (which fills in missing data segments before searching) successfully flagged all 14 expected pre-merger signals, with inpainting holding up even when three one-day gaps were punched into the final two weeks of data. When multiple mergers crowd the same time window, iteratively subtracting already-identified signals lets quieter ones emerge. The results map out the practical pipeline steps needed for real LISA multi-messenger operations.