AAS Meeting #193 - Austin, Texas, January 1999
Session 42. Gamma-Rays/Gravitation
Display, Thursday, January 7, 1999, 9:20am-6:30pm, Exhibits Hall 1

## [42.03] On the Nature of the Broad 1.809 MeV Feature Observed by GRIS

S. J. Sturner, J. E. Naya (USRA, NASA/GSFC)

Recent observations of the Galactic Center region by the GRIS balloon-borne germanium spectrometer have determined that the diffuse 1.809 MeV emission resulting from the decay of 26Al has an intrinsic width of 5.4 keV FWHM. This line width indicates that the 26Al is either at a temperature of ~4.5\times 108 K or it has a nonthermal velocity of ~500 km/s. Previous authors have suggested that for the 26Al to remain at this large a velocity over its 106 year lifetime it must be trapped within dust grains in the ISM (see e.g. Naya et al. 1996, Chen et al. 1998). In this poster we discuss the results of our model for the initial acceleration of the 26Al in dust grains as they exit their source, a Type II supernova, and their subsequent reacceleration in the ISM by ambient supernova remnant (SNR) shocks. Our results show that dust grains can be maintained at a velocity sufficient to explain the GRIS observation for ISM densities of ~0.2\ {\rm cm-3}, dust grain sizes near 10-5 cm, and distances between SNR shocks in the ISM of 100 - 200 pc.