Binary and multiple-star systems are now recognized as a fundamental component of stellar astrophysics. Observational studies have shown that at least half of solar-type stars reside in binaries, while the multiplicity fraction of massive stars approaches unity. Because many of these systems interact during their lifetimes, binary evolution plays a central role in shaping the life cycles of stars.

Binary interactions, including mass transfer, tidal evolution, common-envelope phases, and stellar mergers, can dramatically alter the structure and evolution of the stars involved. These processes give rise to a wide range of astrophysical phenomena that cannot be explained within the framework of single-star evolution. Examples include interacting systems such as Algols and symbiotics, chemically peculiar stars, blue and yellow stragglers, as well as evolved systems such as non-spherical planetary nebulae, intermediate-luminosity transients, and X-ray binaries. Binary evolution is also crucial for understanding some of the most energetic events in the Universe, including supernovae, gamma-ray bursts, and compact-object mergers that produce gravitational waves.

Over the past decade, the field has experienced remarkable progress driven by both observations and theory. Large surveys and facilities, such as Gaia, TESS, and major spectroscopic and time-domain surveys, have revolutionized the census and characterization of binary and multiple systems across the Galaxy. At the same time, observations with JWST are providing unprecedented views of binaries in embedded star-forming regions and in distant stellar populations, opening new windows on the early and late stages of binary evolution. Meanwhile, gravitational-wave observatories including LIGO–Virgo–KAGRA have revealed populations of merging compact binaries, providing a completely new probe of the final stages of binary evolution. The next generation of facilities, including the ELT, the Vera C. Rubin Observatory, and others, promise to further transform the field through unprecedented time-domain coverage.

In parallel, theoretical work has advanced significantly. Modern stellar-evolution calculations, population-synthesis models, and multidimensional simulations of key interaction phases are providing new insights into processes such as mass transfer, common-envelope evolution, and stellar mergers. Nevertheless, many fundamental questions remain open, including the physics governing binary interactions, the formation channels of compact binaries, and the role of binaries in shaping stellar populations and transient phenomena.

The third meeting in the Impact of Binaries on Stellar Evolution (ImBaSE) series aims to review the progress achieved in the past five and ten years and to discuss the future direction of the field. This meeting will bring together observers, modellers, and theoreticians working across all aspects of binary and multiple-star evolution, and aims to foster collaborations within the community as we enter a new era of data-rich stellar astrophysics.
 

A few of the key topics to be addressed include:

• Binary and multiplicity statistics
• Formation and evolution of binary systems
• Interacting binaries and their products across the HR diagram
• Impact of higher order multiplicity
• Modelling binary systems and their interactions
• Binaries in resolved and unresolved populations
• Progress allowed by large surveys and facilities
• Open questions in binary evolution

The list is open, and participants are encouraged to propose other related topics, enriching the conference's discourse. The conference program remains dynamic and will be shaped by the SOC based on the abstracts submitted by participants.
 

For any questions, please feel free to contact the organisers (Ana Escorza, Jaroslav Merc & Michael Abdul-Masih) via the conference email: imbase2027@iac.es.