The LISA-Taiji network: precision localization of massive black hole binaries

TL;DR

The paper proposes a space-based gravitational-wave detector network combining LISA and Taiji to significantly improve the localization of massive black hole binaries, aiding electromagnetic follow-up and cosmological measurements.

Contribution

It introduces the LISA-Taiji network concept and demonstrates its potential for four orders of magnitude better localization accuracy using Fisher matrix analysis.

Findings

Achieves about four orders of magnitude improvement in localization.

Enables host galaxy identification prior to black hole merger.

Supports use of black hole binaries as standard sirens.

Abstract

A space-based gravitational-wave detector, LISA, consists of a triangle of three spacecrafts with a separation distance of 2.5 million kilometers in a heliocentric orbit behind the Earth. Like LISA, Taiji is compose of a triangle of three spacecrafts with a separation distance of 3 million kilometers in a heliocentric orbit ahead of the Earth. They are expected to launch in 2030-2035. Assuming a one-year overlap, we propose the LISA-Taiji network in space to fast and accurately localize the gravitational-wave sources. We use the Fisher information matrix approach to analyze the sky localization for coalescing massive black hole binaries. For an equal-mass black hole binary located at redshift of 1 with a total intrinsic mass of $10^5 M_{\odot}$, the LISA-Taiji network may achieves about four orders of magnitude improvement on the event localization region compared to an individual detector. The precision measurement of sky location from the gravitational-wave signal may completely identify the host galaxy with low redshifts prior to the final black hole merger. Such the identification of the host galaxy is helpful for the follow-up change in electromagnetic emissions of the accretion disk when the massive black hole binary merges to a single massive black hole, and enables the coalescing massive black hole binaries to be used as a standard siren.