Gamma-Ray Limits on Galactic [TSUP]60[/TSUP]F[CLC]e[/CLC] Nucleosynthesis and Implications on the Origin of the [TSUP]26[/TSUP]A[CLC]l[/CLC] Emission

The Gamma Ray Imaging Spectrometer (GRIS) recently observed the gamma-rayemission from the Galactic center region. We have detected the 1809 keVGalactic 26Al emission at a significance level of 6.8-sigma but have found noevidence for emission at 1173 keV and 1332 keV, expected from the decay chainof the nucleosynthetic 60Fe. The isotopic abundances and fluxes are derived fordifferent source distribution models. The resulting abundances are between2.6+-0.4 and 4.5+-0.7 Solar Masses for 26Al and a 2-sigma upper limit for 60Febetween 1.7 and 3.1 Solar Masses. The measured 26Al emission flux issignificantly higher than that derived from the CGRO/COMPTEL 1.8 MeV sky map.This suggests that a fraction of the 26Al emission may come from extendedsources with a low surface brightness that are invisible to COMPTEL. We obtaina 60Fe to 26Al flux ratio 2-sigma upper limit of 0.14, which is slightly lowerthan the 0.16 predicted from current nucleosynthesis models assuming that SNIIare the major contributors to the galactic 26Al. Since the uncertainties in thepredicted fluxes are large (up to a factor of 2), our measurement is stillcompatible with the theoretical expectations.Comment: to be published in Astroph. Journal Letters, 12 pages, 3 Postscript figures; added reference for introduction, typos adde