The Critical Role of LIGO-India in the Era of Next-Generation Observatories

Multi-messenger astronomy, driven by gravitational-wave observations, is a rapidly evolving field poised for significant advancements over the next decade. Our work examines the role of the upcoming LIGO-India detector in enhancing multi-messenger efforts, comparing ten network configurations using key metrics such as SNR (ρ), sky localization area (ΔΩ₉₀), and the precision of astrophysical parameter measurements. Our results show that a network with two L-shaped Cosmic Explorer (CE) detectors and one triangular Einstein Telescope (ET) performs best, detecting nearly the entire annual binary neutron star merger population (16,585 events) up to redshift 0.5 with SNR ≥ 10, and localizing over 10,000 events within 10 deg². Remarkably, replacing the 20km CE detector with LIGO-India retains comparable performance, with a similar detection count and localization of over 9,000 events within 10 deg². Both networks can detect Ο(100) mergers up to 10 minutes pre-merger with localization areas ≤ 10 deg², significantly outperforming a network of two CE detectors and LIGO-Livingston. Our findings highlight LIGO-India's potential to improve source localization and extend early warning times, which is critical for advancing multi-messenger astrophysics.