Gravitational-wave Merger Forecasting: Scenarios for the early detection and localization of compact-binary mergers with ground based observatories

TL;DR

This paper assesses the future capabilities of ground-based gravitational-wave detectors to provide early warnings for neutron star mergers, enabling prompt electromagnetic follow-up observations over the next decade.

Contribution

It evaluates the detection and localization prospects of upcoming detector upgrades and concepts, highlighting their potential for early warning and multi-messenger astronomy.

Findings

Design sensitivity can give 18 seconds warning for one source per year.

A+ upgrade can provide 54 seconds warning with localization under 100 deg$^2$.

Voyager concept can deliver nearly 3 minutes warning with precise localization.

Abstract

We present the prospects for the early (pre-merger) detection and localization of compact-binary coalescences using gravitational waves over the next 10 years. Early warning can enable the direct observation of the prompt and early electromagnetic emission of a neutron star merger. We examine the capabilities of the ground based detectors at their "Design" sensitivity (2021-2022), the planned "A+" upgrade (2024-2026), and the envisioned "Voyager" concept (late 2020's). We find that for a fiducial rate of binary neutron star mergers of $1000 ~\mathrm{Gpc}^{-3} \mathrm{yr}^{-1}$, the Design, A+, and Voyager era networks can provide 18, 54, and 195s of warning for one source per year of observing, respectively, with a sky localization area $<$100 deg$^2$ at a $90\%$ credible level. At the same rate, the A+ and Voyager era networks will be able to provide 9 and 43s of warning, respectively, for a source with $<$10 deg$^2$ localization area. We compare the idealized search sensitivity to that achieved by the PyCBC Live search tuned for pre-merger detection. The gravitational-wave community will be prepared to produce pre-merger alerts. Our results motivate the operation of observatories with wide fields-of-view, automation, and the capability for fast slewing to observe simultaneously with the gravitational-wave network.