First demonstration of early warning gravitational wave alerts

TL;DR

This paper reports the development and testing of an early-warning system for gravitational wave alerts from binary neutron star mergers, enabling pre-merger alerts to facilitate rapid multi-messenger follow-up observations.

Contribution

It introduces a low-latency infrastructure within LIGO-Virgo for pre-merger gravitational wave alerts, demonstrated through mock data challenges.

Findings

Successful detection of binary neutron star mergers before merger in simulations

Low-latency alert system capable of real-time operation

Enhanced readiness for multi-messenger astrophysics

Abstract

Gravitational-wave observations became commonplace in Advanced LIGO-Virgo's recently concluded third observing run. 56 non-retracted candidates were identified and publicly announced in near real time. Gravitational waves from binary neutron star mergers, however, remain of special interest since they can be precursors to high-energy astrophysical phenomena like $\gamma$-ray bursts and kilonovae. While late-time electromagnetic emissions provide important information about the astrophysical processes within, the prompt emission along with gravitational waves uniquely reveals the extreme matter and gravity during - and in the seconds following - merger. Rapid communication of source location and properties from the gravitational-wave data is crucial to facilitate multi-messenger follow-up of such sources. This is especially enabled if the partner facilities are forewarned via an early-warning (pre-merger) alert. Here we describe the commissioning and performance of such a low-latency infrastructure within LIGO-Virgo. We present results from an end-to-end mock data challenge that detects binary neutron star mergers and alerts partner facilities before merger. We set expectations for these alerts in future observing runs.