The final stages of binary evolution using multi-messenger studies

TL;DR

This paper discusses how multi-messenger observations combining gravitational waves and electromagnetic signals from ultracompact binaries can revolutionize our understanding of binary evolution, tidal interactions, and supernova progenitors, emphasizing future technological needs.

Contribution

It highlights the scientific potential of joint GW and EM observations of ultracompact binaries and underscores the necessity for advanced spectroscopic capabilities in the 2040s.

Findings

LISA will resolve tens of thousands of ultracompact binaries.

Multi-messenger data can constrain binary evolution and supernova progenitors.

Advanced spectroscopic facilities are essential for future studies.

Abstract

Ultracompact Galactic binaries with orbital periods below an hour are among the strongest persistent gravitational-wave (GW) sources in the mHz band and will constitute the dominant population detected by the Laser Interferometer Space Antenna (LISA). Tens of thousands are predicted to be individually resolved, with a substantial fraction bright enough for electromagnetic (EM) follow-up. This opens an unprecedented multi-messenger window on compact binary evolution, tidal interactions, mass transfer, and the progenitors of Type Ia supernovae. We highlight key science enabled by joint GW + EM constraints and emphasize the critical need for rapid, high-cadence spectroscopic capabilities in the 2040s. In particular, the most compact (<10 min) binaries detected by LISA will require read-noise-free, zero-dead-time spectroscopic facilities, potentially realized through coordinated arrays of telescopes with time-staggered exposures, to measure radial velocities, tidal heating signatures, and orbital evolution with the precision needed for transformative multi-messenger studies.