Angular distribution of 1.809 MeV gamma rays generated in the decay of Al-26 produced by Galactic novae

Diffuse Galactic 1.809 MeV line emission, produced by the decay of the radionuclide Al-26 is modeled for nova distributions. Two distinct nova contributions were investigated: accreting carbon-oxygen white dwarfs and accreting oxygen-neon-magnesium white dwarfs. It is demonstrated that the modeled diffuse emissions, as functions of Galactic longitude, are significantly different for these two nova types. These differences result because, first, carbon-oxygen and oxygen-neon-magnesium white dwarfs can be remnants of different stellar populations, and second, Al-26 production by carbon-oxygen white dwarfs is expected to be systematically lower for novae located in the Galactic spheroid than for novae situated in the Galactic disk. 50 refs