Introductory remarks on the symbiotic star AG Draconis

The Hα profile of AG Dra has a shape which is typical of many of the symbiotic stars. The strong, sharp central peak is bordered by wings of unequal strength. The blue wing of the emission is decidedly stronger than the red wing, a situation commonly referred to as a ''blue asymmetry''. Occasionally, the blue wing developes a distinct shoulder and perhaps even a reversal or separate blue shifted component. Similar phenomena have been reported by Smith and Bopp (1981). They show that the blue component is most pronounced at photometric minimum and suggest that it comes from a wind off the hot component which at that time is less dominated by the redward component which originates around the cool component. Spectra obtained by the author, in which the continuum is well detected and which are linear and unsaturated over their entire intensity range, show that the red peak remains nearly constant relative to the continuum while a distinct absorption cuts into the blue wing. (Auth.)