Early warning of precessing compact binary merger with third-generation gravitational-wave detectors

TL;DR

This paper evaluates how precession effects and Earth rotation improve early warning localization of neutron star-black hole mergers with future gravitational-wave detectors, enabling alerts minutes before coalescence.

Contribution

It provides the first quantitative estimate of localization precision in early warning scenarios considering binary precession effects.

Findings

Localization to 100 deg^2 at 12-15 minutes before merger

Localization to 10 deg^2 at 50-300 seconds before merger

Precession effects significantly enhance early warning localization accuracy

Abstract

Rapid localization of gravitational-wave events is important for the success of the multi-messenger observations. The forthcoming improvements and constructions of gravitational-wave detectors will enable detecting and localizing compact-binary coalescence events even before mergers, which is called early warning. The performance of early warning can be improved by considering modulation of gravitational wave signal amplitude due to the Earth rotation and the precession of a binary orbital plane caused by the misaligned spins of compact objects. In this paper, for the first time we estimate localization precision in the early warning quantitatively, taking into account an orbital precession. We find that a neutron star-black hole binary at $z=0.1$ can typically be localized to $100\,\mathrm{deg}^2$ and $10\,\mathrm{deg^2}$ at the time of $12$ -- $15 \,\mathrm{minutes}$ and $50$ -- $300\,\mathrm{seconds}$ before merger, respectively, which cannot be achieved without the precession effect.