Radioactive 26Al and 60Fe in the Milky Way:: Implications of the RHESSI detection of 60Fe

The recent detection of gamma-ray lines from radioactive (26)Al and (60)Fe in the Milky Way by the RHESSI satellite calls for a reassessment of the production sites of those nuclides. The observed gamma-ray line flux ratio is in agreement with calculations of nucleosynthesis in massive stars, exploding as SNII (Woosley Weaver 1995); in the light of those results, this observation would suggest then that SNII are the major sources of (26)Al in the Milky Way, since no other conceivable source produces substantial amounts of (60)Fe. However, more recent theoretical studies find that SNII produce much higher (60)Fe/(26)Al ratios than previously thought and, therefore, they cannot be the major (26)Al sources in the Galaxy (otherwise (60)Fe would be detected long ago, with a line flux similar to the one of (26)Al). Wolf-Rayet stars, ejecting (26)Al (but not (60)Fe) in their stellar winds, appear then as a most natural candidate. We point out, however, that this scenario faces also an important difficulty. Forthcoming results of ESA's INTEGRAL satellite, as well as consistent calculations of nucleosynthesis in massive stars (including stars of initial masses as high as 100 M(.) and metallicities up to 3 Z(.)), are required to settle the issue.