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Paper: Physical Properties of OH/IR Stars Close to the Galactic Center
Volume: 186, The Central Parsecs of the Galaxy
Page: 389
Authors: Winnberg, A.; Lindqvist, M.; Habing, H. J.
Abstract: Physical properties deduced from OH flux density and circumstellar envelope expansion velocity are studied in a statistical sense for a sample of about 140 OH/IR stars close to the Galactic Center (GC). The sample is confined to an area on the sky of about 1.14 square degrees roughly centered on the GC and the 3σ sensitivity of the survey is about 60 mJy. The distribution of the expansion velocities shows an asymmetric shape with a much steeper gradient on the high vexp side than on the low vexp side. It has a median value of about 18 km s-1 whereas OH/IR stars elsewhere in the Galaxy show significantly lower average expansion velocities. The flux density distributions for OH/IR stars with expansion velocities smaller than (Group I) and larger than 18 km s-1 (Group II) are significantly different. Group I contains stars with higher flux densities than Group II. Although Group I has a more extended volume density distribution than Group II this fact alone probably cannot explain the difference in their flux densities and a real difference in the OH luminosity functions has to be invoked. A complete paper on this project will soon appear in Astronomy and Astrophysics.
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