Observation of the galactic 1809 keV gamma-ray line with the HEXAGONE spectrometer. [Milky Way]

We report an observation of the galactic 1809 keV gamma-ray line produced by radioactive {sup 26}Al in the interstellar medium. The measurement was performed with our high resolution germanium spectrometer HEXAGONE on a balloon flight in May 1989 from Alice Springs, Australia. Our differential spectrum of the Galactic Center region shows a narrow line at 1809 keV corresponding to a flux of (1.9 +/{minus} 0.9) {center dot} 10{sup {minus}4} photons {center dot} cm{sup {minus}2} s{sup {minus}1} assuming a source at the Galactic Center. We discuss the available observations of the 1809 keV line in the context of models that have been proposed for the origin of the galactic {sup 26}Al.