Two-dimensional gas-dynamical modeling of the mass-flow structure is used to study the outburst development in the classical symbiotic star Z And. The stage-by-stage rise of the light during the outburst can be explained in the framework of the colliding winds model. We suggest a scenario for the development of the outburst and study the possible influence of the changes of the flow structure on the light of the system. The model variations of the luminosity due to the formation of a system of shocks are in good agreement with the observed light variations.
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.
Abstract. Broad-band UBV JHKLM 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.
High-resolution data in the region of the Hα line have been obtained at the time of light maximum and after it for the 2006 optical outburst of the symbiotic binary Z And. A blueshifted absorption component indicating an outflow velocity of about 1400 km s −1 , as well as additional emission components with similar velocities, situated on the two sides of the main peak of the line, were observed during that time. It is suggested that all of them are spectral signatures of bipolar outflow, observed for the first time in the optical spectrum of this binary. The emission measure and the mass of the nebular part of the streams have been estimated approximately, reaching values of up to about 6 × 10 57 cm −3 and 8 × 10 −8 M .
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