Dynamical binary interactions in the 2040s

TL;DR

The paper argues that the 2040s multi-messenger era will unlock end-to-end constraints on dynamical binary interactions by exploiting Luminous Red Novae as clean laboratories for CE physics, mass transfer, and merger outcomes. It proposes an integrated program combining state-of-the-art RMHD simulations with high-fidelity, multi-wavelength observations and population-synthesis calibration to connect microphysical processes with population-level statistics. By enabling growth in LRNe identifications and utilizing instrumentation with enhanced angular, spectral, and sensitivity capabilities, the approach aims to measure interaction energetics, geometry, and remnant evolution for hundreds to thousands of events per year out to approximately 150 Mpc. Overall, the work links CE dynamics to the formation of gravitational-wave progenitors and a wide range of transients, bridging theory and observations across multiple messengers.

Abstract

Dynamical binary interactions such as common envelope (CE) evolution or stellar mergers are a critical phase in the formation of a wide variety of binary phenomena, ranging from blue stragglers to type I supernovae (of all flavours, a, b and c), $γ$-ray bursts to bipolar planetary nebulae, Thorne-Zytkow objects to X-ray binaries. In 2040s, the urgency of resolving long-standing questions regarding the physics behind the dynamical interaction stages and the absolute and relative frequencies of binary evolutionary pathways will only increase owing to rapidly expanding population statistics of gravitational wave events. Here, we argue that multi-wavelength observations (spectroscopy and photometry), linear spectropolarimetry, and interferometry of a large number of Luminous Red Novae, a particular class of transients associated with dynamical binary interactions, will provide unprecedented details about the underlying interaction physics. A breakthrough will be achieved by a tenfold or larger increase in identifications of transient-type events from interacting binaries and their follow-up with instrumentation that provides at least 10 times better angular resolution, 100 times better spectral resolution, and $\sim$100 times higher sensitivity than 2030s facilities.

Figures (1)

• Figure 1: From LRNe observations to constraints on diverse binary evolution pathways. The elements of the plot were adapted from the literaturehan20kaminski_ckvullu23kirilov25. The magnifying glass shows the phases of unstable mass transfer leading to binary mergers, and common envelope evolution.