mass ejection from the symbiotic prototype z and during its 2006 outburst

Abstract

High-resolution spectroscopic observations in the region of the Balmer Hα and Hγ lines of the symbiotic binary Z And were performed during its major eruption in 2006. the Hα line had additional satellite high-velocity components situated on either side of its central peak which indicated bipolar collimated outflow from the compact object. the Hγ line presented three components, consisting of a central narrow emission, a broad emission component with low intensity indicating an optically thin stellar wind with a velocity of about 500 kms-1 from the compact object and a blueshifted P Cyg absorption with a multi-component structure occupying a broad velocity range. These data are explained in light of a model where a disk-like envelope surrounding the accretion disk collimates the stellar wind on the compact object and gives rise to bipolar outflow. the mass-loss rate of the accretor was derived at several epochs after outburst. We conclude that the mass-loss rate has decreased probably from 4-5 × 10−7 (d/1.12kpc)3/2M⊙ yr−1 at the time of maximum light to about 2 × 10−7 (d/1.12kpc)3/2M⊙ yr−1 in 2006 December.