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| - Hydrogen and helium emission of the symbiotic binary AG Draconis during an active phase (1996-1997)
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| - High resolutions observations of the regions of the H α and $\ion{He}{ii}$ 4868 lines of the symbiotic star AG Dra were performed during its time of activity in 1996-1997. Profiles, fluxes and radial velocity data of these lines as well as the line $\ion{He}{i}$ 4713 were obtained. The H α fluxes changed in correlation with the optical light. The emission measure of the circumbinary nebula of the system at several epochs during its 1994-1998 active phase was also calculated using Balmer continuum emission on the basis of U photometric data from the literature. It was increased by factors up to 36 above its quiescent maximal value. After the 1996 and 1997 light maxima the profile of the $\ion{He}{ii}$ 4868 line contained a broad emission component indicating mainly a stellar wind from the hot secondary with a velocity of $1100\div1300$ km s -1. The mass-loss rate of this star was estimated to be about $1\div2$ 10 -7(d/1.7 kpc) $^{3/2}~M_{odot}$ yr -1. The growth of its Lyman luminosity however is not sufficient to explain the increased nebular emission during the active phase. A view that this emission could be the result of both a rise of the mass-loss rate of the cool giant of the system and a rise of the Lyman flux of the hot luminous secondary, being in a steady-state burning regime during the quiescence, is discussed.
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