The spectroscopic evolution of the symbiotic star AG Draconis: I. The O VI Raman, Balmer, and helium emission line variations during the outburst of 2006-2008
Abstract
AG Dra is one of a small group of low metallicity S-type symbiotic binaries with K-type giants that undergoes occasional short-term outbursts of unknown origin. The goal is to determine changes in the envelope and the wind of the gainer in this system during a major outburst event and to study the coupling between the UV and optical during a major outburst.
Using medium and high resolution groundbased optical spectra and comparisons with archival FUSE and HST/STIS spectra, we study the evolution of the Raman O VI features and the Balmer, He I, and He II lines during the outburst from 2006 Sep through 2007 May and include more recent observations (2009) to study the subsequent evolution of the source. The O VI Raman features disappeared completely at the peak of the major outburst and the subsequent variation differs substantially from that reported during the previous decade.