OSSE results on Galactic γ-ray line emission

We report progress in an ongoing search for γ-ray line emission from the Galaxy using OSSE. Four lines are of interest. The 4.4 and 6.1 MeV lines from de-excitation of 12C and 16O excited by cosmic-ray impacts, which were detected by COMPTEL from the Orion molecular cloud, have been searched for at several longitudes in the Galactic plane, without success. Constraints can be placed on one specific model of a point-source origin of the lines. The other two lines, the 1.17 and 1.33 MeV lines from 60Fe, may be present at the limit of OSSE’s sensitivity at positive longitudes in the central radian of the Galaxy.