Spectral observations of AG Draconis during quiescence and outburst (1993-1995)

High and intermediate resolution observations of the blue and the Ha spectr al regions of the symbiotic star AG Dra at quiescence and during an active phase in 1994 and 1995 were performed. Variations of profiles, fluxes and r adial velocity data of a number of emission lines are investigated. The wid th (FWHM) of all of these lines was very large at times close to the 1994 l ight maximum. The emission measure of the surrounding nebula was also calcu lated using Balmer continuum emission on the basis of U photometric observa tions from the literature. It turned out that at the times of the 1994 and 1995 visual light maxima the emission measure has increased by a factor of 15 and 8 respectively, compared with its quiescent maximal value. After the 1995 light maximum the profiles of the HP and Hy lines contained a broad e mission component that indicated a hot stellar wind. The velocity of this w ind and the mass-loss rate of the hot secondary giving its rise, were equal to 800 km s(-1) and 210-7 M-. yr(-1). A view that the observed presence of a hot wind and the increase of the emission measure together can be consid ered as an argument in support of the thermonuclear outburst model is discu ssed. Moreover, we argue that a shocked wind region with X-ray luminosity o f about 10 L-. must be present in this system when the hot wind exists.