Aluminium-26 from Massive Binary Stars. I. Nonrotating Models

Aluminium-26 is a short-lived radionuclide with a half-life of 0.72 Myr, which is observed today in the Galaxy via γ-ray spectroscopy and is inferred to have been present in the early solar system via analysis of meteorites. Massive stars are considered the main contributors of ²⁶Al. Although most massive stars are found in binary systems, the effect, however, of binary interactions on the ²⁶Al yields has not been investigated since Braun & Langer. Here we aim to fill this gap. We have used the MESA stellar evolution code to compute massive (10 M . ≤ M ≤ 80 M .) nonrotating single and binary stars of solar metallicity (Z = 0.014). We computed the wind yields for the single stars and for the binary systems where mass transfer plays a major role. Depending on the initial mass of the primary star and orbital period, the ²⁶Al yield can either increase or decrease in a binary system. For binary systems with primary masses up to ~35-40 M ., the yield can increase significantly, especially at the lower mass end, while above ~45 M . the yield becomes similar to the single-star yield or even decreases. Our preliminary results show that compared to supernova explosions, the contribution of mass loss in binary systems to the total ²⁶Al abundance produced by a stellar population is minor. On the other hand, if massive star mass loss is the origin of ²⁶Al in the early solar system, our results will have significant implications for the identification of the potential stellar, or stellar population, source.