An Early-warning System for Electromagnetic Follow-up of Gravitational-wave Events

Binary neutron stars (BNSs) will spend ;10–15 minutes in the band of Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo detectors at design sensitivity. Matched-filtering of gravitational-wave (GW) data could in principle accumulate enough signal-to-noise ratio (S/N) to identify a forthcoming event tens of seconds before the companions collide and merge. Here we report on the design and testing of an early-warning GW detection pipeline. Early-warning alerts can be produced for sources that are at low enough redshift so that a large enough S/N accumulates ∼10–60s before merger. We find that about 7% (49%) of the total detectable BNS mergers will be detected 60s (10s) before the merger. About 2% of the total detectable BNS mergers will be detected before merger and localized to within 100 deg2 (90% credible interval). Coordinated observing by several wide-field telescopes could capture the event seconds before or after the merger. LIGO–Virgo detectors at design sensitivity could facilitate observing at least one event at the onset of merger. Unified Astronomy Thesaurus concepts: Neutron stars (1108); Gravitational waves (678)