A collimated wind interpretation for the spectral variability of Z And during its major 2006 eruption

High-resolution observations in the region, centered at \(\lambda\,4400~\mathring{\mathrm{A}}\) and those of the lines He ii \(\lambda\,4686\), \(\mbox{H}\upbeta \) and He i \(\lambda\,6678\) of the spectrum of the symbiotic binary Z And were performed during its outburst in 2006. The line \(\mbox{H}\upbeta \) had additional satellite high-velocity emission components situated on either side of its central peak. The lines of neutral helium presented two components, consisting of a nebular emission situated close to the reference wavelength and a highly variable P Cyg absorption. Close to the optical maximum the line He ii \(\lambda \,4686\) was weak emission feature, but with the fading of the light it changed into an intensive emission consisting of a central narrow component and a broad component with a low intensity. The lines of N iii and C iii were very broadened. We demonstrate that all of these groups of lines with very different profiles can be interpreted in the light of the same model, where a disc-shaped material surrounding the compact object collimates its stellar wind and gives rise to bipolar outflow.