The Origin of the Galactic 26Al and 60Fe

Abstract

The radioactive nucleus 26Al (1Myr lifetime) was the first cosmic radioactivity ever detected, through its gamma ray emission line at 1.809MeV, with the HEAO-3 satellite in the 80’s. More recently, COMPEL instrument onboard CGRO made the first all-sky map of its diffuse emission in the Galaxy, which revealed that 1.8MeV photons trace the massive star population, but with room to other potential important producers like AGB stars and novae. The SPI instrument of the current ESA mission INTEGRAL has corroborated the detection of the 26Al line with excellent spectroscopic resolution, and has also detected the two lines at 1.173 and 1.333MeV of 60Fe (2Myr lifetime), yielding an observed 60Fe/26Al gamma ray flux ratio which can not be reproduced with current theoretical determinations based solely on massive stars. We will discuss the contribution of the different stellar scenarios to the global 26Al and 60Fe content of the Milky Way and give an interpretation of the recent INTEGRAL observations.