The Hydrogen and Helium Lines of the Symbiotic Binary Z And during Its Brightening at the End of 2002

• Published in: Astronomy reports 2010-06, Vol.54 (6), p.528-536
• Main Authors: Tomov, N. A., Tomova, M. T., Bisikalo, D. V.
• Format: Article
• Language: English
• Subjects: Accretion; Accretion disks; Astronomy; Astrophysics; Double stars; Emissions; Helium; Hydrogen; Observations and Techniques; Physics; Physics and Astronomy
• ISSN: 1063-7729; 1562-6881
• DOI: 10.1134/S1063772910060065

High resolution observations in the region of the Hα, HeII λ 4686, and Hγ lines in the spectrum of the symbiotic binary Z And were performed during a small-amplitude flare at the end of 2002. The profiles of the hydrogen lines were double-peaked, and suggest that the lines may be emitted mainly by an optically thin accretion disk. Since the Hα line is strongly contaminated by emission from the envelope, the Hγ line is used to investigate the properties of the accretion disk. The Hα line has broad wings, believed to be determined mostly by radiation damping, although the high-velocity stellar wind from the compact object in the system may also contribute. The Hγ line has a broad emission component, assumed to be emitted mainly from the inner part of the accretion disk. The HeIIλ 4686 line also has a broad emission component, but is believed to arise in a region of high-velocity stellar wind. The outer radius of the accretion disk can be calculated from the shift between the peaks. Assuming that the orbital inclination can range from 47° to 76°, we estimate the outer radius to be 20–50 R ⨀ . The behavior of the observed lines can be interpreted in the model proposed for the line spectrum during the first large 2000–2002 flare of this binary.