A radio jet in the prototypical symbiotic star Z And?

Abstract

As part of a multi-wavelength campaign to observe the 2000--2002 outburst of the prototypical symbiotic star Z Andromedae, we observed this object six times each with the Multi-Element Radio Linked Interferometer Network (MERLIN) and Very Large Array (VLA). The radio flux varied significantly during the course of the optical outburst at all three observation frequencies (1.4, 5, and 15 GHz). A jet-like extension was present in the 2001 September MERLIN image and appeared to be aligned perpendicularly to the plane of the binary orbit. Assuming that the ejection took place at the beginning of the optical outburst, the 0.06 arcsec separation between the peak of the extended emission and the central core implies that the ejected material was moving with a velocity of \~400 km/s. This extended emission faded on a timescale of ~months and was not detected at any other epoch. We consider the implications of jets being a component of a ``prototypical'' symbiotic system and compare properties of the observed jet of Z And with those of the jets in X-ray binary systems.