Evidence for bipolar jets from the optical spectra of the prototypical symbiotic star Z Andromedae

Aims:We have studied optical spectra of the symbiotic star Z And, obtained during its latest outburst started in April 2006, with the aim of finding changes in the spectrum yielding clues to the nature of the hot component and its outbursts.
Methods: The spectroscopic observations of Z And have been made using the 1.5-m telescope at the Tartu Observatory, Estonia, and processed in a standard way.
Results: We have found high velocity satellites to the hydrogen Balmer emission lines. Starting from July 30, 2006, weak additional emission components at velocities of about ±1150 km s^-1 were detected. Their appearance near the outburst maximum and similarity to the emission features in another symbiotic star Hen 3-1341 imply fast collimated outflows from the hot component of Z And. This finding is consistent with the earlier results by several authors that symbiotic stars can emit bipolar jets at certain stages of their outbursts. A significant decrease in the temperature of the hot component in initial stages of the outburst was detected by the disappearance of the high excitation emission lines from the spectrum.