EDP Sciences
Free Access
Volume 453, Number 1, July I 2006
Page(s) 279 - 293
Section Stellar structure and evolution
DOI https://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)

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

© ESO 2006

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