Unveiling the Gravitational Universe at \mu-Hz Frequencies

TL;DR

This paper proposes a space-based interferometer to detect gravitational waves in the 0 0Hz frequency range, filling a crucial gap in the GW spectrum and enabling new astrophysical and cosmological insights.

Contribution

It introduces a novel 0 0Hz GW detector concept that extends the observational capabilities beyond existing and planned detectors.

Findings

Identifies the 0 0Hz band as scientifically valuable and underexplored.

Shows the detector's potential to observe massive black hole binaries and stellar binaries.

Highlights the importance for multimessenger astronomy.

Abstract

We propose a space-based interferometer surveying the gravitational wave (GW) sky in the milli-Hz to $\mu$-Hz frequency range. By the 2040s', the $\mu$-Hz frequency band, bracketed in between the Laser Interferometer Space Antenna (LISA) and pulsar timing arrays, will constitute the largest gap in the coverage of the astrophysically relevant GW spectrum. Yet many outstanding questions related to astrophysics and cosmology are best answered by GW observations in this band. We show that a $\mu$-Hz GW detector will be a truly overarching observatory for the scientific community at large, greatly extending the potential of LISA. Conceived to detect massive black hole binaries from their early inspiral with high signal-to-noise ratio, and low-frequency stellar binaries in the Galaxy, this instrument will be a cornerstone for multimessenger astronomy from the solar neighbourhood to the high-redshift Universe.