Radioactive 26Al from accretion discs around black holes in the Galaxy




26Al has a lifetime of roughly one million years, much shorter than the Galactic evolution; therefore, observations of 1.809-MeV gamma-rays from its decay show that nucleosynthesis is currently active in our Galaxy. Massive stars are suggested to be the origin of radioactive 26Al, but the uncertainties in predictions of 26Al yields are still quite large and face some important difficulties. Here we show that 26Al can be produced by nucleosynthesis in the hot regions of bimodal accretion discs and outflows around black holes. Our results show that it could contribute as much as (0.3–3) M of 26Al stored in the Galaxy.