Spectral indications of ejection of mass by the symbiotic binary Z Andromedae during its 2000-2002 outburst★

Abstract

High-resolution observations in the region of the lines Hα, He iiλ 4686 and Hγ of the spectrum of the symbiotic binary Z Andromedae were performed in the quiescent state of the system and also during its outburst phase in 2000–2002. The triplet lines of He i had P Cygni profiles indicating stellar wind with a velocity of 60 km s−1 from the hot secondary. This wind created an absorption dip in the emission profile of the line Hγ. The lines Hγ and He iiλ 4686 had a broad emission component, indicating an optically thin stellar wind with a velocity of about 500 km s−1. The intensity of the broad component reached its maximum together with the optical light. To explain the observations, a model with an accretion disc was proposed, where the velocity of the wind from the accretor is supposed to be 500 km s−1. The accretion disc is responsible for the breaking of the stellar wind close to the orbital plane where its velocity decreases to about 60 km s−1. The mass-loss rate of the accretor at the time of a maximal light was obtained of 2.4 × 10−7 (d/1.12 kpc)3/2 M⊙ yr−1 and decreased to 1.0 × 10−7 (d/1.12 kpc)3/2 M⊙ yr−1 in 2001 October.