Binary stellar evolution yields in galactic chemical evolution calculations

¹ Institute for Astronomy (IvS), KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
² Department of Space, Planetary & Astronomical Sciences and Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India

^⋆ Corresponding author: alex.kemp@kuleuven.be

Received: 31 March 2025
Accepted: 19 July 2025

Abstract

Context. Galactic chemical evolution (GCE) models aim to bring together stellar yields and galactic evolution models to make predictions for the chemical evolution of real stellar environments. Until recently, stellar yields accounting for binary stellar evolution were unavailable, leading to an inability for GCE calculations to account for most binary stellar evolution effects. Fortunately, effective stellar yields that account for binary stellar evolution at a population level can be pre-computed and then used as if they were single yields.

Aims. We present a framework for the computation of effective stellar yields that accounts for a mixed population of binary and single stars under an adjustable mix of binary evolution settings: the binary fraction, the accretion efficiencies of winds, Roche-lobe overflow, and supernovae. We emphasise the critical need for more complete yield coverage of the binary nucleosynthesis and evolution, without which the ability to make accurate predictions on the true role of binarity on GCE calculations is hamstrung. We also provide clear guidelines for future stellar modelling works to ensure their results are maximally useful to the wider community.

Methods. We compute effective stellar yields using detailed binary stellar yields accounting for binary induced mass-loss from a solar-metallicity donor star. We study the effect of varying the binary mixture and accretion efficiencies, and consider a range of models for the treatment of accreted material on the secondary in detail.

Results. In the absence of detailed binary yields for the secondary, we put forth a model for the composition of accreted material that preserves the signature of the primary’s nuclear processing within the post-mass-transfer secondary yields. This model includes special treatment for isotopes of the light elements Li, Be, and B and accreted radioisotopes. Among the binary parameters, we find that the binary fraction, which determines the ratio of binary and single star systems, has the most significant effect on the effective stellar yields, with widespread impact across most isotopes. In contrast, varying the accretion efficiencies produces comparatively minor changes. We also find that the binary fraction has a significant influence on the logarithmic elemental abundance ratios relative to H present in the effective yield; this impact is the largest for the lower-mass primaries.

Conclusions. Comprehensive coverage of binary systems is essential for advancing our understanding of the role of binary stellar evolution in galactic chemical evolution. Priority areas include low-mass stellar evolution, binary mergers, and supernova yields coupled with the evolution of their binary progenitors with nuclear post-processing. The low-metallicity regime is also largely unexplored, offering great opportunity for novel and impactful research in this area.