Mass ejection by the symbiotic binary Z And during its 2000-2002 outburst

Broad-band UBVJHKLM data have been obtained at the time of the quiescent orbital photometric maximum of the classical symbiotic binary system Z And, and at some epochs of its 2000-2002 active phase. The data of the active phase are related to the time of the optical maximum and after it when the star was returning to quiescence. Broad-band quiescent RI photometry from the literature was also used to obtain the parameters of the cool component of this binary. All of these data suggest that the hot compact component has undergone a major expansion and the emission measure of the circumbinary nebula has also increased. Some mechanisms for interpretation of the outburst are reviewed.

Based on observations collected at the National Astronomical Observatory Rozhen, Bulgaria and the Crimean Station of the Sternberg Astronomical Institute, Ukraine.