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

• Published in: Monthly notices of the Royal Astronomical Society 2008-09, Vol.389 (2), p.829-838
• Main Authors: Tomov, N. A., Tomova, M. T., Bisikalo, D. V.
• Format: Article
• Language: English
• Subjects: Accretion disks; Astrophysics; binaries: symbiotic; Double stars; outflows; Spectrum analysis; stars: activity; stars: individual: Z Andromedae; stars: mass-loss; stars: winds; stars: winds, outflows
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2008.13597.x

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.