The last three years: multiband gravitational-wave observations of stellar-mass binary black holes

TL;DR

Multiband gravitational-wave observations over the last three years enable detailed parameter estimation, host galaxy identification, and early merger warnings for stellar-mass binary black holes, offering significant astrophysical insights.

Contribution

This paper demonstrates the potential of combined space- and ground-based gravitational-wave observations to precisely characterize stellar-mass binary black holes and identify their host galaxies.

Findings

At least percent-level measurement of all binary parameters.

Potential to identify host galaxies for binary black holes.

Early warnings for mergers enable multi-wavelength follow-up.

Abstract

Understanding the formation and evolution of the stellar-mass binary black holes discovered by LIGO and Virgo is a challenge that spans many areas of astrophysics, from stellar evolution, dynamics and accretion disks, to possible exotic early universe processes. Over the final years of their lives, stellar-mass binaries radiate gravitational waves that are first observable by space-based detectors (such as LISA) and then ground-based instruments (such as LIGO, Virgo and the next generation observatories Cosmic Explorer and the Einstein Telescope). Using state-of-the-art waveform models and parameter-estimation pipelines for both ground- and space-based observations, we show that (the expected handful of) these multiband observations will allow at least percent-level measurements of all 17 parameters that describe the binary, the possible identification of a likely host galaxy, and the forewarning of the merger days in advance allowing telescopes at multiple wavelengths to search for any electromagnetic signature associated to it. Multiband sources will therefore be a gold mine for astrophysics, but we also show that they could be less useful as laboratories for fundamental tests of general relativity than has been previously suggested.