Structure of the hot object in the symbiotic prototype Z Andromedae during its 2000–03 active phase

Free access article

Issue		A&A Volume 453, Number 1, July I 2006


Page(s)		279 - 293
Section		Stellar structure and evolution
DOI		http://dx.doi.org/10.1051/0004-6361:20052917

A&A 453, 279-293 (2006)
DOI: 10.1051/0004-6361:20052917

Structure of the hot object in the symbiotic prototype Z Andromedae during its 2000-03 active phase

A. Skopal¹, A. A. Vittone², L. Errico², M. Otsuka³, S. Tamura⁴, M. Wolf⁵ and V. G. Elkin⁶

¹ Astronomical Institute, Slovak Academy of Sciences, 059 60 Tatranská Lomnica, Slovakia
² INAF Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy
³ Okayama Astrophysical Observatory, NAOJ, Kamogata, Okayama 719-0232, Japan
⁴ Astronomical Institute, Tohoku University, Sendai 980-8578, Japan
⁵ Astronomical Institute, Charles University Prague, 18000 Praha 8, V Holesovickách 2, Czech Republic
⁶ Centre for Astrophysics, University of Central Lancashire, Preston PR1 2HE, UK

(Received 22 February 2005 / Accepted 2 March 2006)

Abstract
Aims.To investigate structure of the hot object in the symbiotic prototype Z And during its major 2000-03 active phase.
Methods.Analysis of the far ultraviolet, optical low- and high-resolution spectroscopy and ${\it UBVR}$ photometry. Reconstruction of the spectral energy distribution (SED) during the outburst. The Raman scattering process.
Results.At the initial stages of the outburst the hot object was characterized by the two-temperature spectrum (a warm stellar radiation and a strong nebular emission) with signatures of a mass-outflow at moderate (~100-200 km s^-1) and very high ( $\approx$ 1000-2000 km s^-1) velocities. The corresponding structure of the hot object consists of an optically thick, slowly-expanding disk-like material encompassing the accretor at the orbital plane and a fast optically thin wind over the remainder of the star. The disk-like shell persisted around the central star until 2002 August as was indicated by the eclipse effect. Then, a significant dilution of the optically thick material and evolution of a fast wind from the hot star, concentrated more at the orbital plane, were detected. A striking similarity of [ $\ion{Fe}{vii}$ ] $\lambda$ 6087 and Raman $\lambda$ 6825 profiles at/after the dilution of the disk suggests their origin within the interaction zone where the winds from the binary components collide.

Key words: stars: activity -- stars: binaries: symbiotic -- stars: individual: Z And -- stars: winds, outflows

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