New estimates of the contribution of Wolf--Rayet stellar winds to the Galactic 26Al

Abstract

We present new yields of 26Al from Wolf--Rayet stellar winds based on rotating stellar models which account well for numerous observed properties of massive stars. We study the impacts on the yields of a change of initial mass, metallicity and initial rotation velocity. We also consider the effects of a change of mass loss rates during the Wolf--Rayet phase. We show that for surface rotation velocities during the core H--burning phase matching to the observed ones, the quantity of 26Al ejected by a star of a given initial mass and metallicity is roughly doubled when the effects of rotation are taken into account. The metallicity dependence of the yield is, on the other hand, very similar to that obtained from non--rotating models. We estimate that at least about 20% to 50% (e.g. 0.6 --1.4 Msun) of the live 26Al detected in the Milky--Way originates from Wolf--Rayet stellar winds. We show the importance of a good knowledge of the present metallicity gradient and star formation rate in our galaxy for modeling both the variation of the 26Al surface density with the galactocentric distance and the global contribution of the Wolf--Rayet stellar winds to the present galactic mass of 26Al.