Abstract
the information available on V923 Aquilae suggests that this B5 star is a cyclic VIR variable, the cycle being longer than 20 years. Observations of the star made at the Cerro Tololo Inter-American Observatory in July 1980 with a dispersion of 9 A mm -1, have disclosed the presence of three shell absorption components, and suggest that the Ha emission borders may be understood in terms of the superposition of two emission profiles, one flat and very broad, the other one relatively narrow and strong. The behavior of the shell absorption components suggests that we can distinguish in the extended envelope three regions where these components are formed: - an outer layer expanding at -40 km s ', - an inner layer expanding at -20 km 1 , and - a layer closer to the star that displays a positive Baimer progression. The Balmer decrements that characterize the emissions imply that the flat, very broad feature must form outside the region responsible for the strong and narrow component. Moreover, turbulence must be at work in that outer region. The regions where the emissions originate must, therefore, be different from the ones that relate to the shell absorption components. Further observations are planned, including spectra in the ultraviolet.
